I don't think Naruto will get an eye power up, that's reserved for Sasuke. Naruto gets the bijuu power up and Sasuke gets the eye power up. Personally I think Kishi wants to pretty much keep Naruto like he is. I think Kishi wants to have Naruto finish the series the way he stated it, still a jerk at times only more mature with some confidence and the acceptance of his comrades. Smarter in the sense that he knows he doesn't have all the answers.
I think that was the point of the sage saying that it was time for the blue eyed boy that would call the name of the 9 beasts and play with them. Naruto is going to be what he always was, a jinchuriki, just more so because he has all of the beasts now. Sasuke will get another eye power up too but I don't think it will be rinnegan.
Rinnegan is the sages power, which Madara is not supposed to have. I don't think that he will give either one of them the rinnegan because it is too close to his and his mother's power. Madara's thirst for this power is where things went wrong. While the sage is leaving the outcome in Naruto's and Sasuke's hands, they are equal now and only together will they be strong enough to beat Madara. Only together are they equal to Madara's current power level.