It'll be epic, but I'm 99.9% sure it'll end in a draw with Sasuke finally changing his mind and coming home.But i am pretty darn sure that the final Naruto-Sasuke fight will be epic too.
Regarding Naruto, I reckon it should be nearing the end of the full story. As they progress, they find out more and more about Naruto's past and now we're basically at the root cause of everything (i.e. Madara). Once Madara's down, the only possible villain I can foresee is Kabuto/Orochimaru...but it would be really silly to continue the story with him as the next antagonist, Sasuke will surely end him at around the same time as Naruto ends Madara.