This is the current, most sensible theory that I've gathered from reading everyone's posts on here (well, almost everyone) and from my own conclusions.
Kishi has obviously placed many hints along the way that Tobi is Obito, from the anagram in his name to the flashbacks of Kakashi.
Due to the questionable plotholes and Kishi's complex style of making things different than what they originally seem (and also unexpected plot twists- ex., Itachi murdering his clan for Konoha vs. for arbitrary selfish evil reasons), the only plausible explanation so far is that Tobi is more than one person.
How could Obito fight Minato even though he was so young? The Tobi that was fighting Minato during the Nine Tails' attack must have been Madara, or some other Uchiha.
How did Obito survive being crushed by a rock? We never see him actually dying in that chapter; therefore, we cannot assume he died. He has lines/disfiguration on (his) right side of the face where he was crushed, another hint that this Tobi is Obito.
Remember how basically everyone was convinced that Tobi was Madara way back when, until Kishi mind****ed us all and revived the real Madara via Edo Tensei? I haven't really seen anyone mention this, but I feel like this detail might be a little important. There HAS to be some connection between the two. As someone else mentioned, Madara may have served as some sort of mentor to Obito as he kind of did to Sasuke and manipulated him.
Obito could be really carrying out Madara's plan/will; otherwise, it doesn't make sense why Obito would be the one who wants control.
There are still many unanswered questions, however...
Another theory is that this figure could also be the Sage of the Six Paths. After all, he does have the rinnegan, sharingan, and as others speculate, probably DNA from both the Senju and Uchiha clans. But where did he come from?
I don't know why everyone's pissed at the thought of Tobi being Obito. I don't think Kishi would ever make things that simple. If he does, then he'll just make up for it with some awesome explanation later...
Kishi has obviously placed many hints along the way that Tobi is Obito, from the anagram in his name to the flashbacks of Kakashi.
Due to the questionable plotholes and Kishi's complex style of making things different than what they originally seem (and also unexpected plot twists- ex., Itachi murdering his clan for Konoha vs. for arbitrary selfish evil reasons), the only plausible explanation so far is that Tobi is more than one person.
How could Obito fight Minato even though he was so young? The Tobi that was fighting Minato during the Nine Tails' attack must have been Madara, or some other Uchiha.
How did Obito survive being crushed by a rock? We never see him actually dying in that chapter; therefore, we cannot assume he died. He has lines/disfiguration on (his) right side of the face where he was crushed, another hint that this Tobi is Obito.
Remember how basically everyone was convinced that Tobi was Madara way back when, until Kishi mind****ed us all and revived the real Madara via Edo Tensei? I haven't really seen anyone mention this, but I feel like this detail might be a little important. There HAS to be some connection between the two. As someone else mentioned, Madara may have served as some sort of mentor to Obito as he kind of did to Sasuke and manipulated him.
Obito could be really carrying out Madara's plan/will; otherwise, it doesn't make sense why Obito would be the one who wants control.
There are still many unanswered questions, however...
Another theory is that this figure could also be the Sage of the Six Paths. After all, he does have the rinnegan, sharingan, and as others speculate, probably DNA from both the Senju and Uchiha clans. But where did he come from?
I don't know why everyone's pissed at the thought of Tobi being Obito. I don't think Kishi would ever make things that simple. If he does, then he'll just make up for it with some awesome explanation later...