Theory (Naruto , Rinnegan , Sage of six paths, Uzumaki's)

[Honord Sage]

What do you get when all the tail beast are in you and you combine Sage and beast mode?Acer The SO6P and who keeps looking more like the SO6P with each upgrade? Naruto Uzumaki is the Acer.

 

[Transcendence]

By the way, it was stated about the Renningan that "it was a blessing that came down from the heavens in times of great despair," so I doubt it was the Juubi who gave him his eyes.

This is a blunt assumption on my part: Obito and Madara are able to control the Juubi because of the Rinnegan and the control is further amplified through the use of Hashirama's cells which strengthen the bond. If the SO6P already had the Rinnegan why didn't he just control the Juubi? Answer: He didn't have the Rinnegan during his bout with the Juubi. Instead he sealed it and thanks to his immense life force (Similar to that of the Uzumaki's) was able to harbor the burden of being the Jinchuriki of the strongest being in the world. The Rinnegan manifested on to the Sage while the Juubi was inside him. And if the assumption of Naruto being the next coming of the Sage ends up being true then having the Rinnegan is just fulfilling said prophecy.

In response to your last statement: Is this not a time of despair? The Sage said that once the Juubi comes again it signaled the end of the world. Perfect time for the Rinnegan if you ask me.

Although not a natural occurrence, Nagato's Rinnegan came about during a Great Ninja War, which in its own way was a time of despair.

 

[SIR HERDERP PRESIDERP SDO]

Honestly, what can the Rinnegan do at this point with two rinnegan-using maniacs like Obito and Madz + Juubi hanging around?

 

[S A G E]

Making the sage an uzumaki would make it the strongest clan and if kishi really wants to make Naruto as the incarnation of the sage, then that's the only way.for Naruto to have the power of sage, he needs the rinengan, and seeing nagato a fellow uzumaki able to use it makes sense.