As far as I know, 3 classes have officially been announced thus far.
And they are...
Witch Doctor (Necromancer replacement)
Barbarian
Wizard

If Diablo 3 follows the initial pattern of the 2nd game, that leaves 2 more classes available for launch. With 2 casters and one heavy melee class, I think it's safe to say that an amazon (ranged/melee non-caster) class is a safe bet, perhaps under a different name. That leaves room for one more, and probably is the more difficult of the 2 guesses. The other remaining classes (including the Lord of Destrucion Expansion) consisted of the Paladin, Druid, and Assasian. (All are essentially hybrids offering melee or caster/ options) Of these three, I'd prefer the paladin to return, but would probably be more interested if they ventured somewhere with a new class altogether...
Being able to play as an Archangel or something? (Out there I know, but shaking things up a bit would be nice, I think they made the right step with the druid class in LoD)

I don't know about all of you, but I would have preferred the older necromancer cosmetic over the new witch doctor...  I'll have to wait and see though! :)

As far as I know, 3 classes have officially been announced thus far.
And they are...
Witch Doctor (Necromancer replacement)
Barbarian
Wizard

If Diablo 3 follows the initial pattern of the 2nd game, that leaves 2 more classes available for launch. With 2 casters and one heavy melee class, I think it's safe to say that an amazon (ranged/melee non-caster) class is a safe bet, perhaps under a different name. That leaves room for one more, and probably is the more difficult of the 2 guesses. The other remaining classes (including the Lord of Destrucion Expansion) consisted of the Paladin, Druid, and Assasian. (All are essentially hybrids offering melee or caster/ options) Of these three, I'd prefer the paladin to return, but would probably be more interested if they ventured somewhere with a new class altogether...
Being able to play as an Archangel or something? (Out there I know, but shaking things up a bit would be nice, I think they made the right step with the druid class in LoD)

I don't know about all of you, but I would have preferred the older necromancer cosmetic over the new witch doctor...  I'll have to wait and see though! :)

Does it really matter? You know your going to buy it, I know I am. ;-D  

Paladin, the others are all Brutes, there's no light, that and the fact he's super popular on D2.

However I'm disappointed to see teleport is still in the game, I hope it's just for evasion.

My Guesses: Another Magic Dude
                         Paladin equivalent.
                         Amazon/Rouge Equivalent
                         Weird, Unorthodox class that we never see coming (Like the Archivist from the April Fools joke)
                       

I can't back this up with a source, but I believe Blizzard has said there will be no Paladin in Diablo III, which bums me out and piques my interest at the same time; it'll be interesting to see what they replace them with.

The Range non caster class will probably happen. I want a morphing class like druid. That was pretty awesome! . Hmmmm Archiveist needs to be in that game... Quest bolt was so funny!

One will be a ranged/druidic/assassin type character I think.ie. just a mix of those three classes to create the game's ranged class.eg. a ranger with a pet,bow(gun maybe) and cloak/shadow skills.

Second character will be a holy (paladin esque) class.Maybe predominantly melee with both dark and light forces , sort of like the Paladin in the Median mod.

I liked that Blizzard went on a little bit of a creative angle with the Witch Doctor and I suspect they will do the same with the second class you refer to.  I wouldn't be surprised to see more than 2 more classes through really.

Who knows?  Wait and see.