well, i have been wondering the same thing, and i do really believe that Sasuke's decision is what ganna favourite one part of the running Fight ( Kakashi+Gai+Naruto+Bee VS madara+Obito).
these two parties will give us a hell of a fight, and it will wear them out completely, and it will go down to which Part sasuke is ganna support when he joins the fight!!
will he carry on in the Uchiha Hatred Path, or he will join Konoha's will of fire!
And whoever he is seeing now ( The one who knows everything) will be big factor in his decision.