IMO, if they kill Revan, it'll be a stupid decision. Reason why is, for me, if they didn't want the Revan character involved in the story, then they should have just not had him involved at all. period.
i don't see the point in bringing a popular character back from the first game, only to use his death to portray how "dark" the second game is. it seems rather pety and unimaginative. it would be an indication that they couldn't come up with their own way to portray a dark story without resorting to killing off a character that Bioware built.
Of course this is just my personal feeling, but IMO the only two options Obsidian should really contemplate are 1)leave Revan out of the story completely or 2)Include Revan somehow, but keep him alive by the end of it.