Personally, I wouldn't mind seeing some levels unrelated to the story of the Force Unleashed, but related to the films. Call them "Classic Adventures" or something. I'd love to be Luke on Tatooine (maybe jumping around on skiffs over the sarlacc)... or possibly the final scenes from ESB.
I know a level or two with Han is too much to hope for... considering the premise of the game is about the force. Although, seeing this engine used for other star wars games or levels set in the movie continuities would rock (IMO).