Anyway, wasn't it said somewhere that Madara's the one that created the tailed beasts? Might be an ability of the sharingan, like how Itachi created the huge robotic monster. So if he did indeed create the monsters, the sharingan should be able to control all of them, not only the 9-tail.
He didn't create them. He just controlled the Kyuubi to attack Konoha.
Also, I just realized something that almost certainly seals the 8 Tail Guy as a survivor.
He seems to be in somewhat control of his beast while transformed, as he's able to converse with Sasuke and his crew, which is something that could greatly assist Naruto. Either that or his beast just happens to be friendly towards it's prison, which is possible since he calls it his partner. But then again, he does seem to be able to go the limit without needing the beast butting in and taking control to do so, as well, he can revert back to himself effortlessly(did so when we first saw him.)
Both are still things Naruto cannot do, but this guy can teach him. Infact, he seems to be the
only Jinchuuriki to have this much control over his beast. Nii lost it when she released hers. Gaara couldn't regain control once he gave Shukaku full access without an outside force. Naruto loses out over the Kyuubi's will at 3 tails and above.
I mean look. Sasuke was fucked
before this guy started using his beast. And he pretty much dove head first to full release. Theres no fucking way they can win. Even his I Win button failed him.
I think Sasuke will be forced to retreat, and say something in regards to Naruto and the Kyuubi, which this guy'll pick up on. He'll go to Konoha to find Naruto, only to end up saving the day against the battle with Pein and Konan. After which, he'll start teaching Naruto how to keep in control.