i read somewhere that its going to end at tobi being revealed. but this is just a rumor.
That would make so much sense as well as all Ninja Storm games need somewhere epic to end, Ninja Storm 1 ended with Sasuke gone, Ninja 2 ended with Pain Invasion and Generations ended with the hint of Sasuke VS Naruto. Lets hope for this, because that means we get edo characters and Madara at some point.
To be honest I kind of feel they'd put Madara in it anyway even if it hadn't got up to that point in the anime as so many fans want him and he's already an established character. If they can put in Hashirama despite not being in Shippuden why not Madara?