In the A Song of Ice and Fire book series, the Night King is more of a myth, like Azor Ahai, instead of an actual character as he is in the show. Because of that, some book fans have speculated the Night King will be reborn, and if Reddit user theDarkLordofMordor's theory is correct, then Jon is destined to fulfill that role. Even though the books and the show's versions of the White Walker storyline are quite different, it's not beyond the realm of possibility that Jon could be the Night King. He's shown that his bravery can be a dangerous thing for him and those he loves. What if his most foolhardy plan of all is having Bran help him travel back to the war between the First Men and the Children of the Forest in order to take the place of the original Night King?
The Three-Eyed Raven was capable of accompanying Bran on jaunts through time, so it may well be within Bran's power to show someone else the past — or make them a part of it. This would add a devastating twist to the tale if it led to Daenerys killing Jon as the Night King, proving that she is the Prince or Princess Who Was Promised after all by mirroring how Azor Ahai forged his flaming sword by plunging it into the heart of the woman he loved.