I just found this video on youtube.
http://www.youtube.com/watch?v=cWaq6Pc8drM
In it, he claims that their are six classes:
Dragon Knight, Templar, Sorcerer, Warden, Night Blade, and a sixth unknown class.
Does anyone have any info on the Warden, Night Blade, and the sixth class?

Warden was removed and replaced with Sorcerer.

Really? From what I heard, Sorcerer was offensive mage and Warden was defensive.

Warden was in the game, but according to the last Press Event (week before Pax) the Warden class was removed, as they felt it was to similar to the Sorcerer. Defensive by trait would be the Templar, as it as native healing bonuses or abilities.

OK, I know they still haven't said anything about the Night Blade, but is there any word on the last unnamed class yet?

None, I doubt we'll hear anything until closer to E3. A new class is a pretty big announcement they'll more than likely save for than

i thought it was confirmed that there would only be 4 at launch. so, DK, T, S, NB. no word on NB yet. but i think it's safe to assume a rogue/assasin type. also remember that the classes are almost pointless with the skill system.

eh, I wouldn't say "pointless" as the class tree can very much have a large effect in how you play your class, but yeah classes aren't a huge factor in your characters role.

Didn't seem like he was providing up-to-date info on the matter, I'm pretty sure there's still going to be the original 4 at launch.

Was just going to say the same thing. Maybe your Dragonknight will cast spells but don't expect to match a Sorcerer. I think people will be disappointed when something like the best Summons are not available to all classes.

Not a huge effect, but not pointless, anyone can be a healer, but as dedicated healers go, a Templar will make the best dedicated healer. as with Sneaky/Stealth toons would be best as a Nightblade, Sorcerer for the caster, they all slight bonuses to each class. So not a HUGE impact but defiantly not pointless