A Few silly theories....
Danzou
yeah thats a good point!, Danzou seemed to know alot about the uchiha and senju, and he seemed to search and desire for their true power!
there is a reason why danzou knew so much about the uchiha and senju, that reason havnt been explained yet, which means its gotta be explained in the future!, will it be explained by tobi or someone else like ressurected orochimaro?, or will it be explained by danzou himself?, i think danzou used shisuis eye to fool both tobi and sasuke and us fans into thinking he was actually dead!!
he Genjutsued us fans!! lol
i dont think danzou is really dead!!, and as we know, danzou seemed to have a history with orochimaro!, perhaps at one time he and orochimaro helped eatchother, and olso worked together!, they both desired the uchiha power!, although it is strange that danzou got sharingans and first hokages DNA while orochimaro was left with nothing!
perhaps orochimaro desired the real power of the uchiha and not just a copy like kakashi and danzou!, maybe orochimaro knew a secret, maybe there was a limit to how much power you could get if you were just a copy, contrary to having the actual body of the uchiha!!
and since orochimaro desired true power and not something that just looks like it, he desired to take over itachis body, later on sasukes!!
danzou implanting fist hokages DNA, only orochimaro have been successful in doing that until now, "with yamato", its most likely that orochimaro implanted it for him!
or it could have been alittle different, and since danzou was a thief, maybe he stole the information from orochimaro!, or maybe they made a deal and exchanged somethings!
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if the coffin kabuto showed tobi contained "the sage of the six paths body", then one of the possibilities could be that tobi is the spirit of madara inside some body like obito or shisui!, tobi said to kabuto: "where did you get that??" , and kabuto told tobi now you cant refuse!
perhaps he said that, because he knows how much tobi needs the sage of the six bodies "complete" body, the sage of the six paths body was different than any other bodies, because it is the source and the combination of both the "uchiha and senjus" - most real and most original power!!
if tobi is a spirit of madara inside a body, perhaps he could use the rinnegan to put himself in the sage of the six paths body!
using the same jutsu that he plans to revive the tentailed with!
i mean i dont think reviving the tentailed and sealing it inside of himself is th only thing tobi plans to do!, its very possible that having the tentailed beast sealed inside of himself will regenerate his body completely!, although not sure about his eyes!, and still his body wouldnt be the same as the sage of the six paths therefore he would be far inferior to him!!
thats why im saying he would need the sage of the six paths body to be complete with the tentailed!!, kabuto may have it, that jerk!
tobi does seem to soon get a rinnegan, he did say afterall, "lets collect the rinnegan", poor konan, i really really hope that she doesnt get killed!!, but tobi will definetly get the rinnegan!!
im almost sure that he needs the rinnegan for his plans!!
although there is a slight possibility that tobi has actually a stockpile of the rinnegan hidden in his dimension!! a freakin stockpile!
i mean if you could create something like izanagi with all those sharingans on even a normal person, imagine if tobi had the tentailed in him and the sage of the six paths body and several rinnegans implanted on his body!! he would be stronger than the sage of the six paths!!
it would make sense for him to be stronger in the end battles, because, if he wasnt, them the sage of the six paths would always remain the greatest, in the manga, and naruto wouldnt have the chance to beat someone even stronger than him!! perhaps both sasuke and naruto together!!
sasuke will most likely die saving naruto!
sakura will die saving hinata!
jiraya and orochimaro died, tsunade left!
sasuke and sakura died, and naruto left!
maybe, just maybe someone will use the rinnegan "possibly the sage of the six paths spirit, or maybe chakra like minato and kushina" to revive either just those who died in the last battle with tobi, or everyone who ever died in the manga!!
and they all live happily ever after!!
a narrator, perhaps with naruto or kakashi, or jirayas voice will tell the ending something like "naruto accomplished his dream and became hokage, and he saved his friend!, and he got the girl "unworthy stuped bitch sakura", or perhaps "worthy hinata", and naruto was hokage for a long time and until he passed over the title of hokage to konohamaro!
with his family and clan revived, sasuke will go home and see his mother, father and his brother itachi are alive and well!, he starts crying and hugs them alltogether!!, the 7th hokage naruto uzumaki makes sasuke the head of the uchiha clan, and they olso live happily ever after!!
or
sasuke and sakura die, and sasuke just like kakashi, he will see his mother and father and brother are waiting for him!, "saying sasuke...., we have been waiting for you!!, sasuke crying and saying, oh, i missed you so much....