I don't think Naruto would be able to keep up with Madara. He could barely even fight Obito, and that was when he was at full strength.
No one can, but right now, it's up to Sasuke for this moment, but knowing Madara is still missing an eye only screams "A hold up before the main event begins". But when you go back to Obito's fight, there was hardly chances for Obito to communicate others. It only happens when they have to think of something, which is why Obito managed to use the time to talk trash to Minato before Naruto went sage and hit him. Madara won't have time because Naruto will be like all annoying to him. I mean he did smack him when he was playing with Bijuus. Put it this way, if you want to talk to non-Naruto, kill Naruto.
Well the combination of Senju and Uchiha powers is what gives you the rinnegan and Hashi did just share his power with Sasuke. So maybe he gets the rinnegan, maybe he just gets a way to separate Hashirama's chakra from Madara.
Plus, you need to be near dead, or at least that's how Madara said it. Hm, if he obtains it, that rinnengan could be bad news for good side wise because from what I remember, that eye is like a war eye, thirsty for kills. We'll see. I feel like you need to have a natural body to maintain your cool. Use it often and it can make you psychopath.