Realizing that Daenerys cannot be burned, the Night King will encase her in a block of ice. The little blue children will visit her in a museum about this period in Westerosi history. She'll be like a Hitler exhibit.
Probably bitter because of all the death there will be, and how sad and melancholic whoever sits on the Iron Throne lives all his/her life with after the events. ANs seet because at least there will be someone left alive.
Just like Aegon III. The Gurm has always likes things repeating in "history".