Revan's dead. Listen to his last words. I just finished playing the Foundry and he said "The Darkness takes me. Now I know how you felt, old friend." (Not the exact words, but close enough) He's dead. But if they do bring him back it should be as a spirit. Someone to guide us in the final battle with the Emperor.
Thats ur opinion. Until Bioware either outright says Revan was killed or he appears again, we don't know what happened to him after the foundry.