Make the call! The next 4 classes released are...

[bringthenoise001]

1). Rageblood Barbarian - Striker

2). Warlock - Ranged Striker

3). Assassin - Striker

4). Ranger - Ranged Stiker

[syberghost]

First off, since there's a Nature skill in game that's not assigned to anybody, we know they're going to release something before long that has that skill. So that tells you probably Ranger or Druid. Since Druid is PH2, and they'll likely stick with PH classes in the beginning until they've got at least two options in each role (Tank, DPS, and Healer), we can logically assume Ranger is forthcoming.

Now let's look at what primary and secondary roles they're covering:

Great Weapon Fighter: DPS/Tank
Guardian Fighter: Tank/DPS
Control Wizard: Controller (AKA Ranged Tank)/rDPS
Devout Cleric: Healer/rDPS
Trickster Rogue: DPS

DPS is pretty covered. Healer isn't. Tank is better than Healer, but less covered than DPS.

So, after Ranger, they need more Heals and Tanks. That makes Paladin the obvious next choice. So, I'd say first we'll get:

1) Two-blade Ranger. (DPS/extra companion is Tank, DPS, or Heal)
2) Protecting Paladin. (Tank/Healer)

At that point, melee is saturated, and some more range is desperately needed. We've left out two base classes entirely, but Warlock doesn't fit the "builds are classes" mechanic very well, and whatever this is they're already working on it, so they probably aren't going to do a "pick your pact" mechanic this early, so we probably skip Warlock some more and go with:

3) War Wizard. (rDPS/rTank (aka controller))

Now it's time to go off the track. All those disappointed Mastermind players from CoH are clamoring for pet classes, and sticking with the "builds are classes" mechanic means Warlocks and Warlords, which are fantastic choices in a pen and paper game where special effects are key, would be Borelocks and Borelords if implemented as-is in an MMO, so we introduce our first true pet class:

4) Infernal Warlock. We make him just like a Mastermind; his pets do all his damage, and he just supports them. Effectively, this makes him (DPS/Healer).

[iamtruthseeker]

I'm going scourge warlock, an uncertain build melee ranger but likely two sword style (marauder or two sword build,) Virtuous Paladin and that's it. If forced for a fourth class, I'd expect Bard but not sure what build. Personally rather see it next. I'm also expecting Half Orc and Dragonborn for races, and am hoping for a future Eladrin but not expecting them first though.

[nordveig]

Seriously can we please have the bard. How can you have a Neverwinter game without a bard?

[shiaika]

I'm also expecting Half Orc and Dragonborn for races, and am hoping for a future Eladrin but not expecting them first though.

As much as I like Dragonborn, adding extra races based on "Human with ....." seems easier for Cryptic. An Eladrin would seem easier to get than a Dragonborn, which would feel more like expansion material.
imho

[enderlin50]

1.) Pursuing Avenger
2.) Isolating Avenger
3.) Avening Paladin
4.) Swordmage

[klangeddin]

1) Defender - Protecting Paladin
2) Striker - Archery Ranger
3) Controller - Predator Druid
4) Leader - Cunning Bard

[irtu]

Ranger (with a skill tree that you can put points to be either range or melee)
Paladin
Monk
Druid

[deathssickle]

Archer Ranger Scourge Warlock

[babylon]

Derp Ranger
Tone Deaf Bard
Shifty Monk
**** Hippie Druid