I think both Naruto and Sasuke will come out of this alive and with a power up . Madara is still out there, stronger than ever and there is no one left to defeat him .He will likely go to take his second eye and possibly fight Kakashi and Minato while there so I don't think that is where Gaara is going .
The only possible things for Sasuke are rinnegan or , more likely , since now he is no position to refuse , Orochimaru might use the curse seal on him again , which would also save his life .
For Naruto , I really hope it's not the other half of Kurama and hope he never gets Kurama back at all , not sealed inside him anyway . That would also make sense since he is supposed to free all tailed beasts in the end. There's no point in resealing the fox only to free it again later and put his life in danger again . This will also make it that when he will fight Sasuke , if it will still happen at all , he will be fighting with his own power . I think his power up , and what will save his life too , is something So6p related , as others have said .
Now really....
Its very annoying saying that (if it ever happens) naruto must fight Sasuke with his OWN power...
Kurama is a PART of naruto (dont forget Bijuus are a mass of chakra) , like the Sharingan is a PART of Sasuke.
A FAIR fight would be Naruto(without Kurama) and Sasuke without his Sharingan
( why not?? since naruto doesnt have his type of "Sharingan" = Kurama?)
So dont say Naruto with his OWN power, since Naruto and Kurama ARE one person together...