The Juubi is currently being controlled by Madara/Obito injecting their own consciousness via roots, similar to how Madara implanted his Will into the Mazou. This raises possibilities... Madara and Obito could either fight for control of the Juubi, or else Naruto could try and insert the Will he received from the other Bijuu, thus giving the Juubi its own consciousness. Personally, I'd like to see both happen.