Once cut by the sword of totsuka, you're sealed for eternity. There's no counter for that. And susanoo is a defence against all physical attacks. Plus with his MS genjustu is useless against him. So his only option is celestial terrablast. Which itachi could undo by his long range attacks in quick succession to destroy the gravity orb.
I thought I saw at the end of the Rose/Madara fight, that the souls of Rose, Nagato, and push/pull guy (sorry, don't remember names well) were hiding out someplace where no one could detect them, and they were formulating a plan.
Wouldn't that mean the possibility of Nagato's return? Maybe that small part of his soul wasn't sealed by the Sword of Totsuka. Kishi could use that plot line, meet up with Naruto and Itachi down the line, absorb enough chakra, and come back to help. Probably by this time, Sasuke would have learned enough from Kabuto and Madara (probably defeated at the end of the war), and incorporated their abilities to be the ultimate villian.
Then the final matchup would be ...
Naruto, Itachi, Bee, Nagato, and the Five Kages
vs.
Sasuke and the resurrected Kabuto, Madara, and the rest of the Akatsuki, and the re-resurrected Jinchuriki (Kyuubi).
How's that for a long range prediction?
