"All of the hints leading up to this being Obito, a chapter titled, "Obito Uchiha", the mask being broken and it showing Obi-****ing-to and the lot of you are still dismissing it ?! Talk about pride, huh? Kishi has never made sense with half of the mangas he writes until later, when he decides to pop out some answers.
Okay, do you all remember when Sasuke resurrected Orochimaru because he wanted to visit "the one who knows everything"? Who is this mysterious new character in the Naruto world and if he/she knows everything, then they must have been around since the beginning. Now, could this man/woman have found Obito? It's possible. Could this man/woman have brain-washed Obito like "Tobi" did to Sasuke? That is also possible. Kishi has proved time and time again that anything is possible and yet all of you dismiss clarities beyond belief.
This "one who knows everything" is the biggest plot-hole in Naruto and could have easily influenced Obito. It is said the Tobi gave the rinnegan to Nagato and that it couldn't be Obito because Obito is younger than Nagato, but could it be possible that the person who gave the Rinnegan to OBITO in the first place, is this mysterious character that Sasuke has gone to see? VERY possible.
Zetsu's ability is regeneration and it is likely that, like Orochimaru and his experimentations, Obito was experimented on to regenerate his face with the Zetsu DNA. This also explains why after being burnt by Amaterasu, he regenerated his arm's tissue. So, we know that OBITO could be infused with Zetsu DNA. Is it also possible that Zetsu's DNA, like stem cell research, could also influence his age? Yes, but people are basing his age off of the fight with the 4th when he summoned the Nine-Tails because he "looked the same". Please don't try trolling with height because during the fight, height could not possibly be distinguished. The mysterious man (keep in mind) could have also taught Obito whatever it was that he needed to know if in fact he is the one that "knows" everything.
I could keep going, but I'll build off of what people reply to this.
Also, no matter what happens; even if Kishi literally says, "It's Obito", people will still conclude irrational reasons as to rule out the possibility. What's so wrong with Obito being the masked man? He seems to have a personal vendetta against Kakashi, as hinted more than a dozen-damn times that he's Obito while conversing with both Kakashi and Guy, said that Guy doesn't remember faces and when you look at the flashbacks of Manga 599, Guy is fighting Obito and loses. Why is Guy fighting Obito the most during recent mangas? I swear, the little things that most of you miss..."