what i am thinking is the main people that will be on the actual battlefield will be.
Hashirama, Tobirama, Minato (maybe depends if he goes back dead after giving his son the gift), Sasuke, Naruto. vs Obito and Madara + juubi.
my reasoning is Kakashi might finally die (Pain arc his father said it wasn't his time yet, foreshadowing this event).
the other Hokages will stand on guard protecting the rest of the shinobi alliance from the juubi's unleashing power.
i also believe that Orochimaru and Hiruzen, karin, suigestu, jugo, the last remaining 4 kages (Gaara, raikage, muu, the chick lol) will return still somewhat injured and bringing back bad news about tsunade as well as her body.
but this is just my idea.