I seriously doubt we will see the "Horadric Warrior" as a playable class. From what I can gather Cain's heir is that young girl we've seen and heard about in some of the trailers/video demos. From these videos, it also seems that she is going to play an integral part as an NPC in the game.
As for what I think the final class will be, I'm torn between a sword/shield kind of guy, and a physical ranged class. Maybe it will be both.