How Minato wins...maybe
This is stretching it, but I'm just gonna go out on limb on this one.
Remember how the Kyubi specifically told Gaara, that the flying thunder god is attached to the seal, and the seal went along withe Kyubi.
But now the Kyubi is with Madara and dark Kyubi is with Black Zetzu is it possible that this is the key for Naruto to get back Kurama as a whole, by somehow Minato using the flying thunder god technique to steal them back in put them into Naruto?
It just an assumption, maybe Minato has some crazy uzumaki seal still up his sleeve.
Or Naruto get Kybui chakra from tools Madara spit out......if the chakra is still in there.