Luke Skywalker will achieve state of oneness with the Force and then take on all three of them.
Seriously, why put Exar Koon as side kick of Luke? He is sith after all.
Luke and Koon will loose simply because for Luke to work with a sith is against his morals.
If it was a jedi with Luke, Mara Jade, for example, then they would win. Jedi can use battle meld, so two of them will fight in unison like one. Sith on the other hand can't fight effectively in a team as they won't trust their life to each other.