Alright Mashima, you've set up a really interesting situation here, now please for the love of god do not drop the ball like you've done so many times in the past.
I know everyone's expecting some epic shit, but I have absolutley no faith in anything remotely interesting or originial happening. Regardless of whose blood that is in the last page, Erza is going to end up winning, probably using something like not fueled by hate as an excuse, then she'll talk Kagura down making her realize the error of her ways without any lasting consequences for either character.
I reallly, really hope I'm wrong, but Mashima lost any benefit of the doubt from me a long time ago.