I don't still believe Tobi is Obito although I have always supported the fact that Tobi is Obito but I am beginning to doubt it.
I think Tobi has d ability to switch faces... If u look at him against Minato, he was light skinned; and the against Konan when his mask was broken he appeared black. when he revealed himself to Kisame, he must have had a different face because Kisame called him Madara... Of which I also think Tobi started wearing masks like Madara to impersonate or resemble him. If u look at the Masked man while talking to Itachi about wiping the clan, he had Madara's long hair and when he control Mizukage, he also had long hairs. I think along the line Madara's time came and they both decided to give PAIN d rennigan since it needed senju chakra to work (uzumaki clan is part of senju and they have red hair so Nagato is an Uzumaki), after which Tobi took over the real Madara's mask as a reminded of his mission and to swap IDs.
I think Obito must have survived that crush somehow, and then he was found by Oro or Madara or even both because Oro seems to know a lot. So he must have been helped with Zetsu body and probably Madara or Izuna senjutsu was poured into him jet like Oro's curse seal, but I don't think its Madara because if it were Madara he wouldn't doubt if Tobi will accomplish his mission. However one thing is clear, Madara knew Tobi, probably trained him as well and discussed his plan for the future.
There is already a huge possibility that Tobi is trying to make Kakashi soft because without Kakashi d battle would be easy for him and he can teleport easily without Kakashi's Kamui interfering. So on that note, I would say Tobi is just pretending to be Obito to soften the confrontation. Tobi is a shape shifter
I believe Tobi still has a lot in his tank, unless there is a plot no jutsu because Tobi does have other powers and he knows so many techniques plus having Obito/Kakashi eye means he can easily copy techniques like Kakashi and we all know that; like Madara, Tobi probably has the Senju cells as well because its clearly planted there in their hideout and he has zetsu as well... so it is clear that Tobi hasn't even started using his powers, may be these guys (Naruto, Kakashi and Guy) are already in a genjutsu, that shouldn't be far fetched for a guy that profusely wants to use infinite tsukyomi (he must have strong genjutsu)
Kishi is just using his genjutsu on all his fans, but with time we will find out d truth