Definitely wants to finish the contract, but the reason for that is a bit of a mystery. He could have retired with fights still outstanding and it wouldn't have changed anything, unless he plans to compete with the UFC somehow, but even then I can't see it really hindering him, unless he wants to fight outside the UFC. I don't see it being about the money, either from a potential contract renewal or from another organization, since he is independently wealthy now. Perhaps it is as simple as he wants to finish out the contract, because he sees that as his word that he would have that many fights, which he kind of alluded to in an interview, if I understood him right.
As for his chances, it is difficult to say. Erick Silva is not a world beater and has been pretty much a can crusher. However, Kos looked lost against Ellenberger after a little early success. I think it comes down to if he can get that takedown and survive the first 6-7 minutes. If he survives that I like him to take a decision and If I was a betting man, I'd be tempted to put a modest sum on him, since he will no doubt be an underdog.