I think madara and obito will mainy get defeated and killed because of plot no jutsu.ok before stating my theory i wud like to point out 3 possible reasons why the theory i am going to give might happen.
1.there's a high possibility that guy and kakashi will die in this war.
2.no one want's to kakashi and guy to die without doing nothing.i i mean they are favourites of many fans so both of them dying without doing anything will not be so good.so i think kishi will kill them after they have done something big.
3.there is no one alive who can defeat madara and obito.
first part:gai attack's obito and he transports his left side to the other dimension and naruto sees it tries to attack but obi transports back into the real world and naruto is brought back too.kakashi has an idea and they split up and naruto, bee takes on madara and kakashi gai vs obito.
ok for madara to die i think its essential for obito to die first.so here is how it's gonna happen.gai goes 8 tails and becomes so fast that it is the same as telapotation.so like minato was able to hit obito gai also becomes able to hit him .so gai catches obito andtells kakashi to hit him with a kamui. Kakashi tells guy that it will hit gai too if he does it while gai is holding obito still.gai tells kakashi that he will die any way because he alredy opened the 8 gate.so kakashi tougens up and kamuis right on onito's head.....split. .obito and gai dies.
after the defeat of obito. Gai falls of to the ground but kakashi already too tired doesn't have any time for a before dead cool talk with gai because on the other hand naruto and bee is holding off madara and pretty much getting stomped by him.kakashi comes top help naruto and tells him that he got an idea.madara makes a perfect susano.naruto fires 2 tbb to the susano and pushes madara back whil stepping back to be out if reach of madara's susano sword.madara realise's that he dosent have time to play and needs the 2 bijju's fast.so madara turns off susano and comes foward for naruto and bee.naruto and bee also charges foward with kakashi a little behind.when madara is close enough to make contact he tries to make susano but kakashi quickly kamui's whole madara in to other dimension like he did it with narutver.
Ok some of u might tell madara is an edo but since he broke the contract with kabuto the edo powers might not be active and even if he is an edo this works too because i did tell that obito had to die first for this to work.so with obito dead no one can bring him back.
GAI GOES 8 GATES.SORRY.