Just a compilation of the classes that have been given a video explanation.  This is for those who may be interested enough in watching said videos, but not actually search for their existence.

Guardian Fighter:

http://www.youtube.com/watch?v=B0_wnyPspNE

Trickster Rogue:

http://www.youtube.com/watch?v=TGbGltNr8lo&list=UUsIghHd1VyG2TEjIKCRU2gw&index=1

Control Wizard:

http://www.youtube.com/watch?v=fekypen93OY&list=UUsIghHd1VyG2TEjIKCRU2gw&index=4

Great Weapon Fighter:

http://www.youtube.com/watch?feature=player_embedded&v=_PWA1unaRCo

At 1:15 of the Great Weapon Fighter video you see a shadowed figure with a bow; it may be the next class that is to be revealed.  In addition, PCGamer has info regarding the Divine Cleric class that should be available in game.  From what I could tell it will be a healing class with AoE and DoTs, able to give up some healing ability to gain more attacks if you plan to play solo.

Originally posted by Yaevindusk

 

At 1:15 of the Great Weapon Fighter video you see a shadowed figure with a bow; it may be the next class that is to be revealed.  ...

Its dusty, a dwarven NPC who accompanies the party.

Ranger however is in the works.

More importantly, you missed the actual sensation in that video, there is one more class there which is out of norm - and is completely unannounced.