This is another of those things that I am not 
entirely sure it's okay to post, so if someone from Wizards of the Coast comes across this and tells me to take it down, I will do so, with apologies. (That said, I suspect a lot more than this has been posted on forums somewhere.) I've posted additional content for warlocks 
before, of course.
This is my attempt to update the warlock class from the 8/17/12 playtest packet to the 1/28/13 playtest packet. I have also proposed some new content and made changes that I think are badly-needed fixes, such as the altered mechanics of Verenestra's first pact boon; I note that WotC has trended more and more away from hit point thresholds for effects as the playtest has proceeded. Other than that, I have reiterated as little of the text from the playtest packet as possible and expanded the warlock class only as far as 7th level, a point I've chosen completely arbitrarily. It was necessary to alter the ritual list to match the revised Spells playtest document. The ritual list is still quite bare, and I hope to see that addressed in the future.
Well, okay, there's one other 
big change. I've overhauled almost every aspect of 
eldritch blast, because I think that it offers an excellent at-will attack, but 4e shows us that at-will attacks of all kinds are far more interesting if you're choosing between two or three different options that are distinguished by something more than range and damage. To that end, warlocks automatically receive 
eldritch blast (or its new variant, 
eldritch blade) and a second at-will attack that does less damage but carries an alternate effect of some kind. It's a shaped force effect, so I thought it would be cool to offer a few other shapes the warlock can assign it. I assume that warlocks would be able to pick up more primary and secondary forces by spending Invocations Known slots. The one other thing that I think warlocks need in a big way is an option internal to the class that supports allies in some way, but I haven't come up with a good idea for that yet.
Likewise, why
 not let warlocks have a melee option? One of my few deep regrets from my time PCing 4e is that I didn't get to play with the hexblade warlock. Since I'm taking it for granted that WotC would eventually get around to re-releasing such a class or class option, I've posited one form of it here.
Because I'm treating the eldritch attack options as shaped mystical weaponry, it makes sense to me to grant the warlock an expertise progression identical to the cleric's, but restrict that expertise to 
eldritch blade and 
eldritch blast attacks, as well as related secondary forces.
Finally, a plotline in Aurikesh has put me in need of powers for infernal warlocks, so I've sketched out what a pact with Graz'zt might look like. This pact is built more on Aurikesh's idiosyncratic interpretation of Hell than on a pure interpretation of 
Graz'zt in D&D canon, but then my knowledge of same is limited to the linked Wikipedia article.
Warlock
Creating a Warlock: When you create a character whose first class is warlock, you gain these benefits.
- Ability Adjustment: +1 to your Intelligence, Constitution, or Charisma score.
 
- Starting Hit Points: 6 + your Constitution modifier
 
- Armor and Shield Proficiencies: Light armor
 
- Weapon Proficiencies: Simple weapons, rapier, scimitar, short sword, hand crossbow
 
THE WARLOCK
| Level  | 
Hit Dice  | 
Weapon Attack  | 
Spellcasting Bonus  | 
Invocations Known  | 
Spell Level  | 
Class Features | 
Arcane Damage Dice | 
Martial Damage Bonus | 
| 1  | 
1d6  | 
+0  | 
+1  | 
3  | 
1  | 
Eldritch Lore, Pact, Invocations, Ritual Magic | 
 | 
 | 
| 2  | 
2d6  | 
+0  | 
+1  | 
4 | 
1  | 
 | 
 | 
 | 
| 3  | 
3d6  | 
+0  | 
+1  | 
4  | 
1  | 
Pact Boon | 
 | 
 | 
| 4  | 
4d6  | 
+0  | 
+2  | 
5  | 
2  | 
 | 
 | 
 | 
| 5  | 
5d6  | 
+0  | 
+2  | 
5  | 
2  | 
Pact Boon | 
 | 
 | 
| 6  | 
6d6  | 
+1  | 
+2  | 
6  | 
2  | 
Arcane Expertise | 
1d6 | 
-- | 
| 7  | 
7d6  | 
+1  | 
+2  | 
6  | 
3  | 
 | 
1d6 | 
-- | 
Eldritch Lore
Choose a Knowledge skill: arcana, forbidden lore, or planar lore. You are trained in that skill.
Pact
Verenestra
- Level 1 Benefit: When speaking to a creature that can understand you,
 you can spend one of your patron's favors to gain greater influence 
over the creature, provided it understands your language. If the target 
fails a Will saving throw, you impose the charmed condition on the 
creature. You can sustain this charm as long as the creature can see and
 hear you, and you can end this effect at any time. Until you end this 
effect, you cannot refresh the patron's favor that you expended on this 
ability. If you or any of your companions harms the charmed creature in 
any way, the charm ends, and you cannot use this skill trick on the 
creature again for 24 hours.
 
- Level 3 Benefit: As a reaction, you can impose disadvantage on a melee attack made against you by a living creature. This costs one of your patron's favors (a proposed clarification of existing text).
 
- Level 5 Benefit: As an action, you can spend one of your favors to 
teleport up to 30 feet to a location that you can see. (Unchanged)
 
Graz'zt
- Level 1: Through your pact with Graz'zt, you channel some of his 
retribution. When you gain this boon, your footsteps leave a trail of 
acrid smoke whenever you walk on ground sanctified by any good or 
neutral deity.
 
- Benefit: When speaking to a creature that can understand you, you can
 expend one of your patron's favors while explaining one of your 
target's sins or moral failures. If the target fails a Charisma saving 
throw, you impose the frightened condition on the creature. You can 
sustain this condition as long as the creature can see and hear you, and
 you can end this effect at any time. Until you end this effect, you 
cannot refresh the patron's favor that you expended on this ability.
 
- Level 3: Graz'zt's malevolent green gaze looks out through your eyes.
 
- Benefit: As a reaction, you can make a magical attack against any 
creature that deals damage to you with a melee attack or a spell. If 
your magical attack hits, the target takes 1d10 acid damage from wounds 
that mirror those inflicted upon you. This costs one of your patron's 
favors.
 
- Level 5: When you increase your pact with Graz'zt to this degree, your teeth become yellowed and sharp.
 
- Benefit: As a word of power, you can spend one of your 
patron's favors to pronounce a curse of destruction against a single 
opponent within 50 feet that can see and hear you. The target rolls a 
Charisma saving throw. On a success, the target takes 1d6 additional 
damage from your weapon attacks and magical attacks for one minute. On a
 failure, the target takes 2d6 additional damage instead.
 
Level 1: Invocations
You gain the minor invocation 
eldritch force, plus 
two additional invocations of your choice, which can be minor or lesser.
 To use a lesser invocation, you must spend one of your patron's favors.
 Minor invocations do not require you to use your favors.
Baleful Utterance - Lesser Invocation (Unchanged)
Breath of Night - Lesser Invocation: Every nonmagical flame within 50
 feet of you is extinguished. A flame is unaffected by this magic if it 
is larger than a fire typically borne by a torch. You also gain 
darkvision with a range of 60 feet for 1 minute. By expending additional
 favors, you can extend this darkvision to allies within 60 feet, at the
 cost of one additional favor per two allies.
Eldritch Force - Minor Invocation: When you learn this ability, you gain one primary force and one secondary force.
Primary Forces:
- Eldritch Blast: Make a magical attack against a creature within 
50 feet of you. If you hit, the target takes 1d10+4 force damage.
 
- Eldritch Blade: You manifest a blade of crackling eldritch energy. 
It is a one-handed finesse weapon that deals 1d8 piercing damage. Use 
your weapon attack modifier to make attacks with your eldritch blade.
 
- Edited to Add: I talked to Kainenchen about this, and in retrospect I think that making this a weapon attack is probably not one of my better ideas. Feel free to read this reference as well as references in Secondary Forces as melee-range magical attacks rather than weapon attacks. 
 
Secondary Forces:
- Eldritch Chain: Make a magical attack against a creature within 
15 feet of you. If you hit, the target takes 1d6+2 force damage, is 
pulled to a square adjacent to you, and ends any invisibility effects.
 
- Eldritch Ram: Make a magical attack against a creature within 50 
feet of you. If you hit, the target takes 1d6+2 force damage and is 
pushed 5 feet away from the direction of the attack (typically in a 
straight line from you). Prone creatures take 2d6+2 damage instead, but 
cannot be pushed; a creature may choose to fall prone as a reaction 
after a hit but before damage is applied. On a critical hit, the push is
 doubled.
 
- Eldritch Bands: Make a magical attack against a creature within 50 
feet of you. If you hit, the target takes 1d8+2 force damage and its 
speed is reduced by 10 feet until the end of its next turn.
 
- Eldritch Shatterblade: Make a weapon attack against an adjacent creature with your eldritch blade. If you hit, your eldritch blade shatters, its shards piercing your target. Your target takes 1d6 piercing damage every round until you reform your eldritch blade
 as a free action. The creature can also end the effect with an act of 
will by making a Wisdom saving throw against your normal saving throw 
DC.
 
- Eldritch Curseblade: Make a weapon attack with your eldritch blade
 targeting an adjacent creature against whom you have advantage, but not
 disadvantage. You may give up the advantage to cause your opponent to 
have disadvantage on all saving throws for one minute, in addition to 
taking normal weapon damage.
 
- Eldritch Defender: You manifest a shield-like force from your 
offhand. It grants a +1 bonus to AC that does not stack with an actual 
hand-held shield.
 
Ethereal Stride - Lesser Invocation (Unchanged)
Fabrication of the Weave - Lesser Invocation (Unchanged)
Shadow Veil - Minor Invocation (Unchanged)
Visage of the Summer Court - Lesser Invocation (Unchanged)
Level 1: Ritual Magic
Warlock Spells
Level 1:
Comprehend Languages
Identify
(Proposed: ritualized version of Disguise Self)
Level 2:
Augury
Knock
Silence
Level 3:
Speak with Dead
Level 6: Arcane Expertise
Your extensive training in eldritch forces makes you deadly on the battlefield.
Benefit: You gain the following features.
Weapon Attack Bonus: You gain a +1 bonus to your attack roll when you're using an 
eldritch blade or related secondary forces. This bonus increases as you gain levels.
Arcane Damage Dice; You gain a single arcane damage die, a 
d6. As you gain levels, you gain additional arcane damage dice. When you
 hit a creature with an 
eldritch blade or 
eldritch blast
 (or related secondary forces), you can spend any number of your arcane 
damage dice. Roll those dice, and add their total to the damage dealt by
 that attack. Some feats and features grant maneuvers, which are fueled 
by arcane damage dice. If you know a maneuver that can be performed with
 your 
eldritch blade or 
eldritch blast, you can spend any of your arcane damage dice on it, rather than on extra damage.
Arcane Damage Bonus: At higher levels, you gain a bonus to 
eldritch blade and 
eldritch blast damage rolls, as well as related secondary forces. Starting at 18th level, once per turn when you hit a creature with an 
eldritch blade or 
eldritch blast attack, you can add a +5 bonus to the attack's damage against that creature.