Fans would nor have will never, never, ever, ever, be happy with his 'final fate'. It could end with him grabbing the Emperor and pulling him into a volcano to finally end the war and people would still be unsatisfied that he is dead. At the same time if he was left alive they would be complaining he doesn't do ENOUGH if he was still alive and kicking.
BioWare shouldn't have included him - personally - at all in my opinion. The odd quests here and there like the Revanite chain would have been good and left an air of mystery surrounding him. It felt like they just threw him out there as fanwank and killed him off just to say "There, you got your Revan and now he's dead. You can shut up about it".
Some people are playing this game BECAUSE of Revan - they just want to find out want happened to hero they played in previous games. Not including him would be a big mistake that would be met with disappointment from many KotOR fans and BioWare knew/knows this. :P
Still, I agree that not fully explaining character's final fate is good ending - it leavs fans to wonder what happened to him and they can imagine it themselves. Imo they should create awesome quality story in TOR related to Revan and than somehow leave his fate unexplained once again when the game is closing in to it's end. Killing him, as you said will still be met with some people's frustration.