The idea that Brienne dies in TWOW doesn’t make any sense to me. Sure, GRRM can do anything he wants, but I would be really disappointed if the true knight challenging stereotypical gender roles in Westeros wasn’t around for what GRRM considers the true war, the War for the Dawn. It would also feel really anticlimactic to me for Brienne to have been given this magic sword that’s one of the few weapons that works against the Others and then, well, NOT be there to use it against the Others.
If Brienne is Dunk’s descendant and one of Dunk’s greatest acts of heroism was saving a ton of people from a huge magical fire, it would be a great nod to the series title if Brienne saved a ton of people during the magical ice apocalypse.