I don't see it happening. The Old Republic and everything surrounding it makes a KotOR III irrelevant. The answers we were looking for after we played KotOR II have mostly been answered through TOR and those novels (even though the answers may not be satisfying).
I say, leave that particular timeframe and start anew somewhere else. If Obsidian wants to dabble in the Star Wars universe again, let them choose another period in Star Wars continuity to craft their story. I rate their chances for that slightly higher than a KotOR III (let's say, pretty much not going to happen?).