Click here to see the hidden message (It might contain spoilers)
Frankly, I think he should have died at the end of the novel Revan, because he really contributes nothing to TOR besides to be the boss at the end of a flashpoint. Bioware's attempts to shoehorn Revan into TOR as a result of their hero worship of him is precisely why he has a bad ending.
Otherwise, if he's so awesome, just have him kill the Sith Emperor in the novel and don't make TOR. Revan had his great ending at the end of KOTOR, they didn't need to keep at it because unless the player character is Revan again, having him be the hero is pointless. I'm actually glad that TOR didn't copy WoW, and just when you're about to kill the Sith Emperor, Revan appears and kills him instead, so after you do all the hard work you don't actually do anything.
I mean, look at The Elder Scrolls III: Morrowind. The protagonist is the Nerevarine, and in the two sequels, Oblivion and Skyrim, there's a mention that after Morrowind, the Nerevarine led an expedition to Akavir, another continent, but hasn't been heard from since. I don't see the issue with Revan's fate just being completely ambiguous. The man saved the Galactic Republic after nearly destroying it at the behest of the Sith, and then disappeared in the Unknown Regions. We can conclude anything we want about his fate. But Star Wars fans won't let Star Wars ever operate like that.