next game is easy
you go after revan as the exile
you find out what hes plotting as the new leader of that sith empire
back in 'known space' you must defeat revan
If you read up on star wars history, Revan leaves to go fight the 'real sith' but then he ends up being their leader.
Which is whom I'd figured that you'd end up fighting at the end of KIII as the exile.