*possible spoiler* Sasuke manages to do some alternate way to get the rinnegan (Plot no jutsu), Sasuke challenges Naruto to see who is truly stronger while everyone else is busy with obito, madara, and juubi, Naruto or sasuke wins (personally doesn't care), due to the prolonged battle juubi absorbs kyruubi/kurama and hachibi,Juubi gains 1 more eye from the hachibi and 2 from the kyruubi (Kurama has 2/10 of the juubi's chakra) thus the juubi goes from 6 to 9 not counting the middle iris which makes 10, Naruto feels hopeless to do anything, sasuke as a last resort to beat the completed juubi gives naruto his eyes, Naruto now being an imperfect sage of the six path (Narutro's an uzumaki and doesn't posses all the traits a TRUE senju has), nauto isn't hindered from using the creation of all things (To a lesser extent than a actual sage), But the juubi is also incomplete (thanks to minato and the bijuus going through some "things" themselves), Naruto fights juubi...etc that's just my theory.