True but their disappearances were different. I find it very unlikely that we will see Revan in form of force ghost. Time will tell but I just have this feeling that we will see more of him IN PERSON for sure.
They would loose alot of subbs if they just killed Revan forever, So to make ppl stay they make him become one with the force and leave a window open for his return as a force ghost. It is sad that they even included him in this game, He should have stayed as he was before, The way we made him to be. The same fore the Exile.