Tobi fought against 4th Hokage...Obito was still just a weak kid that couldn't touch the 4th hokage.
Okay Let's see, we know that Tobi knows Madara, so if indeed it is Obito, he's had like 3-6 years of training by Madara. Remember now, Sasuke had 3 years of training with Oro, and could arguably have beaten Kakashi (Though I have no doubt that he could, just don't want to start a meaningless debate) at the finish of his training.
Now this is Madara, a mastermind. One who achieved the rinnegan, tricked the entire ninja world into believing he was dead, and even planned to be resurrected later in the future. Spending even a year with a mastermind like this could prove very beneficial for the student. Also, let's not forget that he too is a sharingan master. Obviusly so since he achieved the rinnegan. Obito is an uchiha himself, certainly this relation between the two would have a more resulting benefit than the Sasuke and Orochiramu student/teach relationship.
Another thing, what most overlook in that fight, is that Tobi used one tech, or maybe two. What I'm saying is don't judge the skill of a character based on one
powerful tech. That tech is the only reason why the was able to go up against Minato, take that away from him, and it would have been the same as a "kid" Obito. He simply has a convenient ability.
In short, you can't really judge that fight with the Obito that Kakashi knew. Not when he have been a student under Madara, and had one heck of a convenient tech, and only used that one abilty throughout the entire fight.
Next, you're probably going to say: Madara was dead around this time. There's no proof of that. You know what I find strange? The edo tensei is said to resurrect you the way that you died. Yet Madara was resurrected in a young looking age. He looks the same age he did as when he fought Hashirama. Now, we know that he lived on to meet Nagato. But why doesn't he look any older? No matter how you look at it, it's odd. If Madara lived to be old, but then Kabtuo "improved" him (Though there is nothing suggesting an improvement on his age), Madara would have no doubt found it strange that he wasn't in an old body, especially since he was expecting to be brought back by Nagato.
That's another odd thing, why live to become an old man, and then desire to be brought back in that same condition. We know that Madara has planned a lot, and thought of a lot, and he knew a lot. I actually have a theory that in his dying times, he was able to transfer his "energy" or "lifeforce" somehow into Obito before he died. So that he would be resurrected in his "prime". And this transfer increased the age of Obito. I know, lots will call it farfectch, but meh xD
Anyway, who's to say how long Madara lived when he should have been dead before Nagato was even born. I don't know the age differnce between Madara and Onoki, but I do know that Onoki was in the same era as Madara, and he's still alive. And if you subtract the Naruto's age which is 16 years, and the age difference of Kakashi when he was a teen compared to when he was a kid. And you're probably gonna end up with like 20-30 years. Madara could have done it with Senju cells if Onoki could pull it off.
Anyway, that whole Madara thing was just in case you argued "There's no way Madara was alive".
He had two sharingans Obito would have had one.
For this one, when we saw two, this was after the massacre of the Uchiha Clan.
He's extremely old...Obito would be Kakashi's age.
Now we can't just take away the fact that Tobi rolls with a guy named Zetsu. Yeah you're probably saying, "Oh there he goes". Just bare with me, we know that one of Zetsu's abilities is regeneration. No matter what you cut off, he can regenerate it. We see that it appears that Tobi himself has pieces of Zetsu in him. You CAN'T just overlook this. Obviously there's a reason behind this. What else do we know that Tobi has, Senju dna? This implies that his body has been severely operated on. I mean what would happen if parts of Zetsu was to take over someone's body? No one really knows. But aging shouldn't seem too impossible when someone's body consist of so many unusual DNAs. Heck, kabuto just had the freaking sound 5 come out his body. There's already so many strange things in this manga.
And there's clearly an "aging" issue with Madara. Which I already mentioned. It basically proves that age-manipulation is indeed possible.
Obito wouldn't suddenly attack the hidden leaf
This can be countered with the fact that half of his body would have been badly damaged in the incident. He may not even remember who he was anymore. Not to mention potential brainwashing from Madara.
I know some of my points are based on assumptions. But when you view it objectively and with an open mind, you'll see there's a "possibility" that Obito's body may be involved.
Note: I also find it very interesting Kishi has decided to put Kakashi there with Naruto when Tobi may reveal his identity. Like I said, I think there's a great possibility that it will turn out to be Obito's body at least.
) believed at least once that it was a great possibility.
