There will be a big build-up, with a little hope that the Alliance is gaining some ground on Madara. Naruto will unleash his super-rasenshuriken and Madara will absorb it with his rennigan and get a big power boost as well as a morale killer. Madara will start to destroy the alliance. Obito will realize that the alliance can't seal Madara and that it will be easier to stop him if they could just kill him. So Obito will sacrifice himself for the alliance by reviving Madara with his Rennigan. Madara is pleased because he can now attempt to complete his plan, and try to absorb the tailed beasts (maybe with his rennigan or because he is so powerful through the Bijuu's shell again). Naruto will intervene and intercept the absorption of the tailed beasts (fulfilling the Sage's prophesy that they will all be become one again) giving rise to the true rebirth of the So6P. Naruto will beat Madara down, but because he is so OP he will try and win him over instead of killing him. This will give rise to the final conflict between Naruto and Sasuke because Sasuke will likely go against Naruto's wishes and kill Madara while he is distracted with Naruto's TNJ.
(Madara will probably absorb the first hokage during the fight as well)
(Madara will probably absorb the first hokage during the fight as well)