If Kreia being Evil wasn't supposed to be a plot twist, why was her Force Alignment arbitrarily locked at Absolute Neutrality despite the fact that THAT is a total crock? Maybe it's just because you're arbitrarily made incapable of preparing for Kreia's betrayal, say, by having Atton inject a small thermal detonator into her bloodstream...
At any rate, I'd like to see KotoR III be totally unrelated to the events of KotoR I and II, actually. Frankly, I see KotoR II as being some extremely poor design choices. They tacked on an arbitrary new threat despite the fact that at the end of KotoR, there was no need for a direct sequel, basically turned Revan into a gigantic Mary-Sue instead of just a capable strategist who found a nice piece of tech.
However, at this stage, it would be effectively impossible to end the storyline without a backlash from the majority of fans who do not feel about TSL the way I do. However, I hope they wrap up this storyline with KotoR III and then continue to make games. There's a roughly four thousand year period they can use KotoR games for, with plenty of stories that can be told. It's a bit Final Fantasy, but that could be a good thing.
At any rate, since KotoR III should take place exclusively within the Unknown Regions, no planet that has ever been mentioned during KotoR should feature in it. However, I wouldn't be averse to seeing such things as the Chiss or Vagaari, both of which could make interesting allies or enemies.