There is no way the NK is dead. It makes zero sense.
This feels like the Jon Snow killing in season 5 (or end of ADWD). We were all shocked, pissed, and a bid let down. It felt senseless and unfulfilling. But then, when we sat back and pieced it all together, we thought, there has to be something more. There has to be an out. And as many theorized, Melisandre was the out. She brought Jon back from the dead.
In this case, the out evolves around Bran. Bran, as the 3ER, was either turned by the NK into a new NK, or is some combination of a greater evil. A combination of the NK and the 3ER. And as many have theorized, there is a hidden evil side to the 3ER. As Old Nan told us, “all crows are liars.” They are manipulators.
The 3ER is a manipulator. He is now Bran, the manipulator.
This is the final twist of the story. And who will kill this greatest of great evil? The Prince Who was Promised. IMO, Jon Snow.
A few recent pieces of evidence:
It would make for a moronic storyline. This point has been hammered home by many. You can't build this up, and just off him that quickly, without a real challenge. It makes no sense.
The Azor Ahai/Prince that was Promised prophecy isn’t properly fulfilled. While all prophecies are not literal, Arya doesn't fit any of the qualifications (except she is a badass!). That wasn’t the ending.
After the show, in the behind the scenes interviews, Dave never states the NK is dead. In fact, he hesitates and says the NK is "uncreated" by the valyrian steel. This is an interesting choice of words. Could someone else be created, or recreated, as the NK. Did the NK warg into someone else - Bran? So many questions.
During an interview with Jimmy Kimmel, he basically says "no comment" when asked whether or not the white walkers are dead. I know he has to be coy, but he’s holding something back.
Bran is not Bran, he's the 3ER/NK. There is more to what he is doing. He is the great evil. We didn't see the end, it is coming and the prophecy will be fulfilled.