Dany's vision from the House of the Undying in Season 2 suggested it, and we're still going with it: King's Landing is going to be nothing but a smoldering, snow-covered ruin by the end of the show.
I totally forgot about that vision, If its shows the future to come then it means that King's landing is going to be attacked by the White Walkers as well most of the seven kingdoms are going to fall and the North including winterfell will be the first in line.