Rinnegan is not required so far we know the sage had the rinnegan when he gave birth to his two sons but it is not clear if he had it before he sealed the juubi so as of now there is no way in knowing but if he did get it from the juubi that would explain why naruto does not have it as that would indicate its not a uzumaki bloodline trait and something unique to the sage.But as for now my theory stands that the sage became the host for the juubi they became one being and when he gave birth to two sons one took on the spiritual force manifesting in the eyes yin nature and took traits of the juubi while the other took on the life force and took traits of the uzumaki.explaining why people seem to think the senju and uzumaki share more in common then the uchiha when in fact the uchiha just took on the traits of the sages other half which was juubi at the time.So far naruto has the uzumaki blood and a piece of chakra from all the tailed beast making him even closer to the sage then anyone alive right now.