It depends on the user is. If its tobi and madara then yes they would defeat him but if its Pain/nagato I don't think so.
Well lets hope that he do not fuse both Sage Mode and BM because if he does he will have so much on them.
1. His already powerful chakra will be 5x stronger than it is now
2. He will be able to sense them in ways no other ninja can do; chakra, natural chakra, and evil
3. He will be 5x faster, stronger, and ninjutsu oooooooooooh weee
4. He will be able to use Frog Kata which no dojutsu can see which will give be dangerous since his reach will seem almost ghost like. Plus no Rinnegan user can absorb the Nature Energy for they will turn into a Frog Statue
5. Besides all his power ups he will be able to make a TBB fused with Nature Energy which will be 5x stronger. That means whoever gets hit with it even with Susanoo better haul a$$ because it is going to make a big dent to destroy anything in its path.
6. Plus we have to remember that Naruto use the Bijuu Roar which is super powerful and from what we have seen will push anyone back and give him an opening to strike while they are trying to regain their balance or otherwise.
7. He has chakra arms which are already super strong that it crushes rocks, boulders, or mountain almost with ease. Now fuse that Nature Energy and his reach is almost infinite since he can extend his arms to great lengths while also covering those chakra arms with Nature Energy. It will be like an invisible powerful force field that will either destroy whatever is in its way or give you a big hit to the body.
8. Also I can't imagine the jutsus that Naruto can come up with while being in that mode. We have seen the MiniRasenshuriken, Plantery Rasengan, etc. So if he fuses I believes that he will be much more flexible as far as what he could do with either one separately. Or to think bout it what new jutsus can he come up with by mixing the advantages from both modes.
9. He has experience with fighting a Rinnegan user and by mixing both modes he will have a much much bettter advantage over any other Rinnegan user than when he was fighting Nagato.
10. We don't know what Kurama knows about Senjutsu or even if he could produce different results with his knowledge or strength. He seems to have a lot of information extending all the way from when they were fused together as the Juubi so I am sure he knows something about something that would help.
Even right now in BM Naruto still has an advantage because he has experience with fighting a Rinnegan User. Plus he can make Sage Mode Clones who can help in ways that B, can't if he hasn't fused the two modes by then. No one will be able to stop his speed or power either.
