I believe that in the end, It will be a deathmatch between Naruto and Sasuke. Either Sasuke will do something to Sakura, or kill someone else important in Naruto's life, but either way I believe Naruto will end up going 4th tail (or beyond) and ultimately (hopefully) rip Sasuke apart. (I'm actually hoping for an Evangelion like bloodbath of Sasuke being ripped apart, ala Eva unit 1 Dummyplug vs Eva unit 3 Contaminated....Yeah!). But then, that's just assuming that Orochimaru doesn't end up being the main bad guy and taking over Sasuke's body.