I really don't see how it is possible for Bolton to win at this point. Most of his army not only wants to betray him but are just waiting for the perfect time. In addition, his secret traitors in Stannis's army have been revealed. It is also going to be common knowledge soon that the Arya is a fake, which is the only thing he has going for him as far as being leader of the North. More damning to me is what a Bolton win would do to the plot. It would mean the end of Asha, Stannis, and Theon. I really don't see that serving much of a purpose at this point.