Email response from Drew Karpyshyn:
I don't want to spoil too much about Revan in the game, but I'll try to answer your questions. Revan's lines were really just an homage to Darth Malak's quote from KOTOR, though it's easy to imagine he had been a little corrupted after 300 years battling the Emperor's evil.
As for Revan's final fate, you never actually see him die. He just sort of disappears, so we left the door open just a little bit in case we want to ever bring him back.