One wonders as well whether the other two Sith Lords will be as interesting as Darth Sion. Also, it is the nature of Sith to turn on each other at the first sign of weakness, but I doubt they will, because that would be one less enemy for you to defeat. Then again, maybe they will. I think theyre main agenda now has to be elimination of the jedi, their main opposition. Once all jedi have been destroyed, Ill think theyll split apart and attack each other more.