I am not sure if next sage or reincarnation of previous sage but I believe that sage could be reincarnated in naruto time because from what I know six realms are part of cycle of repeated reincarnation(Saṃsāra). I personaly hope that naruto will surpass previous Sage Of The Six Path's because in naruto(manga) there is a important theme about next generation surpassing previous one yet no one surpassed Sage Of The Six Path to prove it truth naruto should completely defeat jubi or something on his level so that's why I hope that naruto will defeat final enemy ALONE because if he wins together with sasuke or someone else then that would mean that he is weaker then Sage Of The Six Path only way to prove then that he is stronger then Sage Of The Six Path would be if final enemy is at least two times as strong as jubi. I also wanted to say that I am not really sure about what was madara talking about Uchiha because he could be lying about it because he was saying before that he is not responsible for kyuubi attack but it is proven false in chapter 500 what I am trying to say is he was saying that senju have half of sage power and the Uchiha second half but maybe it's not true maybe being child of jinchuuriki of strongest biju could have some side effect, that Idea comes from the fact that naruto is BORN with whiskers and when naruto uses kyuubi chakra they become bigger so it proves that there is a connection between kyuubi and whiskers, maybe first child of sage inherited part of jubi power and second child part of sage power, madara told us that uchiha inherited the Sage's eyes and chakra yet kyuubi said that chakra of sasuke is more sinister then his own and there is only one biju with more sinister chakra the jubi also when we look at the eyes of sage he doesn't have tomoe in them only ripples yet jubi have both maybe jubi eye is a fusion of Rinnegan and his orginal eye that would mean that sharingan was born from jubi power also when we look at the sasuke the bigger his hatred the stronger he gets and the biju's are mass of hatred so maybe final battle won't be a naruto(descended from the younger of the two sons) vs sasuke(descended from the elder of the two sons) but a naruto(new Sage Of The Six Path) vs sasuke(new jubi).

Final of naruto(manga) naruto defeats final enemy then creates peace by overcomes circle of hatred by destroying mercenery like ninja system because they were supposed to a guardians not mercenaries create new path for ninja like they were supposed to be in orginal vision of sage, then he should get married have bunch of children have a long life someone should write a book about naruto something like that "legend of naruto, a ninja who surpassed the god(sage of the six path's)" a true happy ending.

ps.sorry for bad english

ps2.sorry for long post