Game of thrones season 7 white walker theory!!!

PART I: WHITE WALKERS:
One of the biggest mysteries in this entire story is the question of what the White Walkers' intentions are.
We know they want to wipe out mankind, but it doesn't seem to only be that, in and of itself. The inclusion of the reveal of how the White Walkers were made in the show is more significant than most think, in my opinion. The fact the Children of the Forest created them isn't only instrumental in understanding why they exist, but also to show why they want to destroy man.
It should be very apparent, that the WWs themselves are George RR Martin's metaphor for weapons of mass destruction. They are Medieval nuclear weapons gone haywire. The COTF made them to fight against man, their bitter enemy. As we know, the WWs, at some point, became too powerful to control, too conscious of their own abilities, and became, essentially, the "monster than took over the lab", so to speak.
But the reason they want to destroy the COtF and man doesn't appear to be solely due to a blind thirst for blood. It seems to be motivated by hate.
And why hate?
Because their existence, is a miserable one...
Becoming a near immortal entity, doomed to live in ice and cold for eternity takes meaning away from their lives. They believe that the circumstances that lead to their creation (war between men and the children) are at fault for their doomed eternal suffering.
But why are they coming back now?
I think it's because they are responding to two things: Jon Snow's birth and the return of dragons. They don't solely want to destroy men and the children...They want to rid the known world of the magic that created them.
How do they do that...?
Well, to get an idea of how this is possible, look at the scene in Bran's flashback to when the first White Walker was created...He had a large shard of dragon glass shoved into his chest.
I think the Night King wants the dragon glass shard pulled out of his chest, possibly by Jon Snow.
What would happen if the shard is pulled from his chest?
He will become human again.
They want to die, in peace, as humans, but not before wiping out as many people as they can.
If they want to die, why not just let Jon Snow take the dragon glass shard out of the Night King's chest? Why do they need revenge in the process?
Because they want to demonstrate that they have not forgotten what happened to them, all those thousands of years ago.
PART II:
BITTERSWEET ENDING:
I believe at least two of the three most key figures in this story, who are instrumental to the Walkers' defeat, must die. These three characters are Jon, Bran, and Daenerys.
If Dany does die, it'll be either one of two ways: 1) At the Wall, fighting the Walkers, or 2) In childbirth, giving birth to Jon's child.
Either way, she will not sit on the Iron throne.
If Jon dies again, I think it'll be through one of two ways: 1) Through a blood sacrifice by fire with the Weirwood trees on the Isle of Faces, or 2) He, himself, will have to take on the role of the new Night King, and return with the wights back to the Land of Always Winter, for eternity, as part of, again, a sacrifice via brokered truce.
If Bran dies, I think it'll be through a reveal that he is the Night King, and that Jon will have to kill him to end the conflict.
The larger scope of the bittersweet climax for ASOIAF is that many will perish, including several main characters. Westeros will mostly be in ruin, with the survivors left to rebuild from the ashes and begin a new beginning.