Shouldn't Naruto be able to regain Kurama's chakra, and Sasuke, his Rinnegan?
Well based on the above facts I could say maybe since most of the time the sharingan users are bound to control a power based on emotions. On his case, true he has the power of Six paths Chakra but when he uses the rinnegan you can witness that he needs to charge it to it's full capacity which is why you could see the Tomoe those dots represents the charged state. So I guess he can bring out the rinnegan in his left eye but will he be able to use it for that I would say it might take time.