He will not come back. I believe the sage will show himself to naruto when he ain't got nowhere to run to. By that being said, the sage stored some of his chakra in kurama that is why he is stronge and naruto wear that chakra robe
I don't think so. He would just easily destroy Madara and Juubi an there won't be any room for Naruto to shine. Besides Hashirama is back so there is no need for more crazily powered shinobi.