I’m guessing they win the battle against the White Walkers and then mobilize south to fight Cersei. Only thing that kind of makes sense and only way it sets up a fair fight, the night king has taken out a dragon before so I assume he can do it again. No way Cersei travels north so the fight is gonna have to come to her
I don’t think they win. Not sure how they get out though. I think this thing ends in King’s Landing.