In the beta he was killed in the foundry fight. Bioware received a bit of flak for it during those days so they made the change to quell the masses. It's still up in the air as to if he will make an appearance again.
I understand why. I like having some closure on that story but a lot of folks are attached to the story of Revan; they want to decide how it ends, not have a character invented (look, gender and all) and told he does x, y and z.
Allow for some ambiguity as to his death and allow players to play a role in the character if he returns.