I don't see him coming back as a complete Edo. I don't believe that Sasuke would be that foolish, especially after finding out that Madara stayed after the Edo Tensei ended. I feel that Sasuke would end up bringing Orochimaru back mostly as just a soul, to talk to him and get information. Sasuke knows this as he saw what Itachi did to him. Itachi sealed him in an never ending genjutsu with his Sword of Kusanagi, so technically he shouldn't be "dead", but living in an eternal genjutsu much like Kabuto right now, only not in the physical world.
Actually the first think Tobi stated to Kabuto about Edo Tensei is that "it could be seen as the most powerful jutsu ever created", Edo Tensei itself can cause the start of entire wars. It is obviously capable of ruling the ninja world by having it. They don't have a stash of DNA at all, and nobody knows that they have this scroll besides Sasuke, Jugo, and Suigetsu. Nobody else knows at all. Does not matter if he is up or on the ground, lets give the old man some respect has been doing better than all the other kages and i dare say the other kages combine. he is suppose to be the one with the least chakra reserve and after weaknessing the terror of perfect susano'o he is still not willing to bare down in defeat but rather die like the shinobi he is unlike that water woman. How did she become a kage anyway ? with such weak resolve after this war she should take resolve classes from naruto that is if she makes it alive. Orochimaru began conducting experiments with Hashirama DNA 26 yrs ago (at Yamato's birth). This was 10 yrs prior to Tobi's fox attack, ~12-14 yrs prior to the Uchiha massacre...where Tobi might've made any DNA-trade with Danzo and thus allowing Oro to get his hands on it. Oro was already kicked out of Konoha by the fox attack though.
Orochimaru is a Sannin of infathomable power, tough enough to escape from Akatsuki without them even caring about him. Most criminal organizations and even villages hunt down missing nin, you do not let a ninja defect to go snitching to other organizations meaning either, Tobi was a bit timid about actually being able to defeat orochimaru.
The chapter was called the "third power." could this mean that orochimaru is also a power in this war himself? We have the alliance, kabuto/tobi, orochimaru? Kishi has finally picked up the pace and maybe we'll see some deaths coming our way. It seems it is called the Third Power because Tobi, and Madara won't be the only ones pulling the strings. Oro is the third power. This really is making me think that Orochimaru knows who Tobi is...Most likely the opposing force of Madara, a Senju...
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