I think Bran is going to summon the red comet (the horn of winter) and smash the wall with it, causing the next long night with the nuclear-winter-style ash. Mayhap he summons the comet by eating Bloodraven. Because in Ragnaroc, the Fenris Wolf must kill Odin, and then swallow the sun, after having been confined to a cave with it's hindlegs tied up by Tyr, the onehanded god of war.

patchface wrote:It's always summer, under the sea
I know, I know, oh, oh, oh
The birds have scales, and the fish take wing
I know, I know, oh, oh, oh
The rain is dry, and the snow falls up
I know, I know, oh, oh, oh
The stones crack open, the water burns
The shadows come to dance, my lord
The shadows come to play
The shadows come to dance, my lord
The shadows come to stay
"Winter is coming" isn't a warning. It's a boast. When you break the rights of hospitality... Winter Comes.