Rinnegan is not Sharingan evolution, but Sharingan is a requirement ONLY if it's merged with Senju's DNA. Telling that Rinnegan is just the Sharingan evolution is a fallacy, a tremendous error. It would be like saying that Rinnegan is the Senju's DNA evolution... it's an incomplete answer.
Proof of this: The Sage is not Uchiha, therefore, the Sage never had a Sharingan to begin with. Also he didn't have Senju DNA's only. He was born with holy's chakra!
And as there was already stated that the Uzumaki Bloodline are connected to the Senju, it's perfectly plausible to think that Naruto could awake the Rinnegan, if not just being compatible with it.
Proof of this: The Sage is not Uchiha, therefore, the Sage never had a Sharingan to begin with. Also he didn't have Senju DNA's only. He was born with holy's chakra!
And as there was already stated that the Uzumaki Bloodline are connected to the Senju, it's perfectly plausible to think that Naruto could awake the Rinnegan, if not just being compatible with it.