here is what i think.
i think he is obito, and the reason why he is still alive is that after he was crushed by a rock, orochimaru recovered him did some freaky experiments on him with zetsu. you guys remember when he was hit by minato's rasengan, his arm was all squishy and falling apart like a clay or something, and also he cut off his hand when he was battling one of danzo's supporters with the bugs. we clearly know that zetsu can merge with the earth and trees, so maybe zetsu also has a type of woodstyle. orochimaru used zetsu's wood style to revive and to immortalize tobi or obito, that being the case we can also recall that the kages were discussing that tobi's immortality was connected to woodstyle. And the scroll suigetsu found might contain the secrets of that immortality jutsu, cause we know that scroll holds something really powerfull. that is my main argument. Another thing i just realized is that obito could have been faking it that he was crushed. he might have used his space-time jutsu to dematerialize his body part that was crushed by the rock, the way tobi always avoids attacks, but i'm not sure about it, its just a guess. The first one I feel very strongly about it, the second not so much. Please reply and tell me what you think.