With the way things are going on the battlefield I'm beginning to think only the SO6P could be able to put an end to the battle. Maybe he should be Edo Tensei'd by Orochimaru or better still Tobirama, the original owner of the jutsu.
Getting Rikudou Sennin in this war at this moment would directly end this war, that person is too powerful. There still needs to be some more struggling, suffering and fighting for the SA and the mates before he'll appear.