(Spoilers Main) What if Dany...

I see a lot of people speculating that Dany is going to bounce back by allying with Jon and using her dragons to win the war against Cersei.

To me, this seems a bit too obvious - GRRM said that the series would have a 'bittersweet' ending. What if that bittersweet ending involved Dany not taking the Iron Throne and instead going North to save Westeros from the White Walkers?