He was pretending to be Madara back then dont get it mixed up we know Tobi didnt fight Hashirama it was Madara all of it was a lie.You must be registered for see images
He will use the juubi's to get in his prime again and he will be the Juubi's jinchuuriki. H esaid that on the 5 kage summit arc, imagine how strong he is in his prime... Wow, and he also have no need for the rinnegan right now.
I believe he is the elder son of Sage, who else would know all this?