I think KOTOR III should mainly be focused on the Exile and Revan meeting up with eachother, or having a third character go out and find them. At some point in the game Revan and the Exile should fight the Sith Empire together.
Meanwhile, I believe some of your KOTOR II party members should stay on Malachor V or Dantioone and start up a New Jedi Order. (The person depends on who is still alive after the TSLRP.)
This is just what I think may happen...