For the love of God, don't "bring back" John Snow. Or anybody else who got it. Stannis. I'd prefer no- and the Stark girl to be dead. Or at least caught and killed by the evil dude.
The thing that makes G.O.T. better than most of the crap out there is exactly that they have steadfastly avoided the happy-ending BS that plagues every sh--ty attempt at modern cinema. It's the same formulaic drivel every time - good guy and/or heroine get away in the end, bad guy meets horrible fate, one or two minor characters die on the way. Bo-ring. Problem with movies is, if you don't make Joe-6 pack and Sally 2 two shoes leave the movie with a smile on their face, they'll post on Facebook what a bad movie it was, and sales crash. This is the Charles Dickens effect. He was the master and modern creator of the obligatory happy ending.
G.O.T. has pulled off a great Coup by being both popular and out of the formula. The best ending in my view would be to have the ice dudes take over the world, killing the blonde woman last. And they keep the dragons as a pet.