See, my only thing that makes me very skeptical against the possibility that the body inside the last casket is Madara's "real" one is because of the simple fact that Madara has placed so much devotion to hiding his identity behind a mask as far back as when he first met Itachi, possibly longer.
If he had placed his essence inside another person's body, then why bother with the masks at all? It's not like anyone would recognize him. And if it was Obito's body Madara had been preoccupying, as I've read some theories supporting, then wouldn't Madara's current "host" be the physique of a small boy, considering that Obito was such when he died?
Kisame knew right off the bat who Madara/Tobi was the second he removed his mask. That, and either Itachi and/or Madara himself mentioned that he had reached a state of "immortality" due to his ridiculous power, so it wouldn't make sense if he abandoned his original body for a younger one.
I don't know... With the way the whole scene was presented, it just seems like there'd be an even bigger, more horrifying revelation lying within that casket than the mere corpse of a supposedly immortal character, such as Madara. But either way, I'm more than excited to find out what it is - even if it, in fact, proves my doubt to be wrong. I'm more than positive that Kishimoto will make it wonderfully shocking.
