This is how predict it will unfold. Events maybe in order/not really.
So right now Kakashi and Obito are off to the other dimension. With this it is undeniable that they will have a fated battle. There is no one other than Kakashi that should fill this roll. His character has suffered burdens all throughout the series, and the results of this fight will lead to his resolution. This transition is also important because we will probably learn why Kakashi killed Rin, and maybe some other facts that will tie in with and explain other shinobi world events.
Sasuke, Oro, Taka, and the Hokage are on the way. I don't predict that they will arrive until the last minute when it seems as though all hope is lost for the alliance. Then BOOOM out of the smoke comes Sasuke and the gang to save the day.
^ This ties in with Kakashi and Obito as well as Madara because of this following
- Minato is bound to meet with his students if but for a moment/he'll learn that he was fighting Obito in Konoha 17 years earlier
- Once Sasuke links the masked man and Obito this is going to piss a lot of people off because.....
^ It's bound to be revealed that Obito had a part in the destruction of the Uchiha clan
^ If Obito hasn't changed sides by this point, the above fact alone should be enough for Madara to kill him
Or maybe once this is revealed Madara will be like ayyyyy though........
^ I killed Rin you little b**h. I put you under a genjutsu.
^ Since we learned that Kakashi and Obito's eyes were linked perhaps they both fell into the same illusion somehow. I can't quite explain my point, but the linkage of the eyes is the main emphasis.