Sasuke will kill Kakashi
I can see Sasuke showing up during or after this current fight, as he has a bone to pick with Tobi. Obviously Tobi tried to manipulate Sasuke, and Sasuke has a poor track record when it comes to forgiveness. I think if Naruto saw Sasuke kill Kakashi right in front of him and realized Sasuke had slaughtered the Konoha elders, he'd be forced to get serious in the final fight.
And besides, Kakashi was "sent back" to take care of something according to his Dad, that's probably dealing with Obito. Once that happens, I can't see all 4 main characters making it out of the series alive. It'd be too happy dappy and not really the sort of darkness we've come to expect from this series.
Consider also that students have a long history of killing their sensei in Naruto. I think it goes without saying Kakashi would try to stop Sasuke from killing Obito and likely fail since Kakashi is basically just a few steps up from fodder at this point. In any case, it'd be a nice setup to Naruto vs Kakashi, Obito vs. Madara. With Kakashi's death, Obito would realize more how evil Madara is and then the Alliance can fight the 10 tails.
Guess there's lots of Kakashi fans on here, but let's keep in mind Kishi has zero problems killing off popular characters like Itachi, the J-man, Tsunade (she won't survive getting cut in half) and others.