Alright, Now from the very begining, since the first time Kabuto showed Madara his Trump Card the 6th Coffin, i had a theory that it was Madara in the coffin, thinking that tobi was only Madaras Soul, and that by showing him the 6th coffin, kabuto revealed to madara that knew who and what he was, because if tobi was only madaras soul in another body somehow, kabuto would have been able to use edo tensei to summon tobi's soul and control him as his puppet!!, and this would show why tobi couldnt refuse!!, but theory has almost been proven wrong, though not entirely nor for certain..
anyway, after seeing this last chapter, i would like to create a list of Possibilities on who Tobi might be!!
List Of Possibilities
1-my old theory might still be true, this way..
if there was more to Edo Tensei than we currently know, forexample..
edo tensei is supposed to be to summon and seal a soul of your desire into a "Strange Body", and that body would become the soul, and have all the powers and abilities it had before its death, what if you could do it the other way around?, to summon a "Strange Soul" into a body of your desire, and instead of the soul being ressurected, the body Will be!!, meaning the strange soul would have all the powers of the body its inhabiting!!, meaning whoevers soul kabuto summoned has now all the powers of uchiha madara!!
2-Zetsu is Madara, half of madaras soul is in black zetsu, taking the shape of madara thanks to white zetsu, black zetsu records or storages the soul, and white zetsu copies the body, after the battle between him and the first hokage, madara put half of his soul in black zetsu, an empty being, looking like dark space, and after the first hokages death, he took his cells and created the white zetsu!!, and with this, he was able to have a body again!!, but he was still not complete, because half of his soul was in the afterlife!!, thats why he said he is only a shell of his former self, and that he wanted to be "Complete", and thats why he said he wanted Nagatos ressurrection Jutsu "Rinnei Gedo Tensei" for the purpose of Revival, and being Complete!!
kabuto summed madara, meaning he had his other half, if tobi hurt him, he would only hurt and weaken himself!!
heres my complete theory of this
3-Madara is the Sage Of The Six Path's Older Son, it explains why he knew so much, and afterall, in any manga or anime, its usually the biggest evil that is the big bad villian, and the Elder Son was the Big and First Evil!!
perhaps he killed his own younger brother, but not before taking serious damage himself!!, he was badly damaged, and he wanted his fathers power, so he set out to collect the bijuu and revive his fathers "SO6P's" true power in himself!!
if this true, this would mean tobi is far older than just a 100 years!!, he is of the time of SO6P, and he knows the bijuu's pretty well, and how to control them, and the only explaination could be this..
So6p's Older son was either the father or Master of Madara, he was madaras master and mentor, and he practicly raised him, and since he loved power, and madara did too, they had alot in common, he truly came to care for the boy!, even evil people have someone whom they truly care about, this could explain tobi's reaction to kabuto's last coffin, and also to his desire to use Nagatos revival jutsu!!, this would also explain why he was able to give nagato his rinnegan, the older son of so6p didnt have sharingan, he had the rinnegan remember?
"perhaps it was even he who took Izunas eyes, and thats why he had sharingan, his own eyes he gave to nagato, then he took about what was originally his"
and if he actually had a son "madara", then it would prove it even more!!
4-Madara is really Obito as so many believed, this may be farfetched, but the only connection could be, that either Zetsu, or Madara saved obito that day, and ever since that day, alot has happened!!
5-tobi is either jyuubi's evil and mind once divided by so6p along with his powers, or it is actually so6p himself!! "though this is only a possibility, im not atall sure of it"