Nah... they won't do that till a few months before release. No release date or anything yet, but it seems, like starcraft 2, it is in a very playable state.
Barbarian, Witch Doctor, and then probably Paladin, Ranger (they were hinted at (we might find out another one tomorrow)), and then Necromancer or Assassin as the 5th class.
Barbarian is about as anti-paladin as you get in terms of RPG's... It's alignment is always in a non-lawful form, and is typically built into a chaotic neutral range, granted in a game like diablo it has leaned more into the chaotic evil alignment.
Though, WoW is getting the Death Knight in Lich King, which is of course, their anti-paladin. So if you want a specific anti paladin, go play that.