Some people believe that their movements are restricted though... like the posters above. In all honesty, when the Juubi reaches its final, and most powerful state, the current Shinobi Alliance have nothing that can sstand up to that sort of power. These 4 have to enter the battlefield to reasonably even out the war.
I believe it'll go down something like this:
1) Hokages break out of Edo Tensei and Minato FTG's them to the battlefield (maybe he's placed a seal on Naruto just in case?)
2) Orochimaru and Taka left by Hokages. Orochimaru sees Sasuke distracted and tries an attack with new-found arms. Juugo and Suigetsu give their lives to protect Sasuke. Sasuke awakes Rinnegan seeing his companions dead. Seals Orochimaru for good with Rinnegan path.
3) Sasuke travelling to battlefield.
4) Hokages + Alliance seem to be winning.
5) Juubi enters final form. Goes nuts and kills everyone. About 20 people left, along with the Hokages. Current Kages come back half-dead after Tsunade gives her life to keep them alive.
6) Hokages and remaining people do most of the damage. Hiruzen + Minato use Shiki Fugin and take Madara + Obito with them (Hiruzen could possibly do this by himself.)
7) Everyone helps out and Naruto finally becomes the Juubi Jinchuuriki.
8) Sasuke reaches the battlefield to find Juubi Naruto, and the others.
9) Sasuke, after learning everything from the Hokages, and understanding friendship after seeing Suigetsu and Juugo die, comes back to Konoha.
10) Naruto made Kage.
11) Naruto wants to fight Sasuke badly, and they fight it out one last time (Naruto suppresses Juubi chakra, as that's ridiculously unfair).
