[ZGoten]

I just read the chapter.

I think by now it is pretty save to assume that both Madara and Obito are/were Tobi. Obito continued what Madara did, because Madara was about to die. Since he needed somebody to continue his work, he entrusted his will to the young boy and made the necessary arrangements to be resurrected at some point in the future. When Obito said that he gave the Rinnegan to Nagato, he was partially right, because it was in fact Madara, who, together with Obito had become Tobi. That means that the story does not need time travel to fill the supposed plot holes that some people think they've found. It makes perfect sense this way. The only question remaining is whether Minato was fighting Madara or Obito. I personally don't believe that it was Madara, though. I doubt he would have been that agile with this old body of his that we see on the last page of the chapter. And this specific panel actually takes place a few years before the fight. However, as james0246 has pointed out a number of times, it wouldn't be anything unheard of in the Narutoverse for characters to gain a tremendous rise in power in just a few years, especially with Madara as your mentor and the Sharingan obviously. So it was probably Obito who fought Minato.

Aside from that, I'm having trouble believing that Madara is/was completely honest with Obito about the idea behind the Moon's Eye plan. I highly doubt that somebody as sinister as him would care about fake world peace. This is probably just his own little mind game to prove to the first hokage that the uchiha were superior all along. 'You can have Konoha, but I'll take the world' - something along that line. He probably used Obito's suffering over Rin's death to gain a follower with the same goal, albeit for a different and in some way even noble reason. Because of this, I think that Madara will have to betray Obito at some point.

/edit:

Very good chapter by the way. Tsunade ... that's some dark stuff. I didn't expect that kind of explicitness and felt really weird for a moment or two.