I personally think it's pretty obvious that Orochimaru and Sasuke together (Orochimaru takes Sasuke's body, so, technically, Orochimaru will be the FV) will be the final villain.
Input on the other "villains": excluding masked Obito, they're all garbage.
To be honest I doubt you can really even call Sasuke the final antagonist. The bout between him and Naruto will be the final source of conflict, but chances r it will be a fight where both already see eye to eye, but they just fight over who deserves more to be the hokage.
Orochimaru will settle out back to the Sound village and revamp the place and plan out his next move for immortality...see this is why Orochimaru was my favorite villain. Even when he lost several times, he was always the first and last main antagonist in the series...