Jon Snow- The Saviour

Jon will make the ultimate sacrifice and become a White Walker himself, as that will be revealed as the only way to actually establish a peace. Perhaps he assumes the mantle of the next Night King (and it would be consistent with some theories that the Night King was once actually a Stark).

I say “peace” because over and over, GRRM has shown in the story that there are no such things as real villains and heroes, so I think it would be inconsistent for the story to conclude with a characterization of the White Walkers as nothing more than opaque mystical evildoers whose worldview we never come to understand. So I don’t think this story ends with the WW’s being defeated or obliterated, but instead with the realization that they are a necessary part of the GoT world, perhaps as part of some necessary balance, and that they have a right to exist as much as any of the other denizens. The showrunners have also hinted that GRRM told them a couple of shocking and surprising plot points, with Hodor’s origin being one and the ending being another, and an ending like this, which subverts a lot of conventional expectations of how high fantasy epics end, seems to fit the bill. It would also really drive home Jon being of both “ice and fire.” The conventional understanding of this is that the “ice” part owes itself to his Stark heritage, and while that makes sense, it’s a slam dunk if he becomes a WW (and is also the kind of sneaky misdirection that GRRM loves). Jon being someone who is, in a sense, already dead, may give him some additional ability to strike a grand bargain by sacrificing himself to the WW’s.

An ending like this also gives more purpose and importance to the Craster subplot - specifically his sacrifice of his male children to the WW’s - in a way similar to Dondarrion’s resurrection was an establishing subplot for Jon’s eventual resurrection. Craster’s sacrifice of his sons establishes that a certain form of sacrifice to the WW’s that results in humans being converted to WW’s will be accepted by them as a token of peace. We haven’t seen any more instances of this principle in the story since that took place, but I don’t think GRRM (or the showrunners) would have put it into the story if it didn’t have significance later. Also important is that in the show at least, Jon actually witnesses this event, so he has a basis for coming up with this as a solution later on.

It also gives more significance to the Children creating the WW as a defense force against men — implicit in this is some notion that the WW’s were originally conceived to re-establish some kind of balance in the world.

Lastly, GRRM has gone on record saying that the ending will be “bittersweet.” It would be a pretty bittersweet ending for our hero, who was born with the right to become king of all Westeros, but treated all life as a bastard, then rises up the ranks to lead the Nights Watch only to get murdered by his own brothers, then is resurrected (and with him feeling conflicted about being resurrected) and wins the Battle of the Bastards, then triumphantly becomes the King in the North and is reunited with his family (presumably Bran and Arya will make their way back into the fold), only to, in the end, have as his reward the sacrificing of his life and humanity to join a joyless gang of icy undead rage-monsters.

As for Dany - I think she ends up being Queen, but not by being the “winner.” It’s highly likely that Westeros and King’s Landing ends up a war-torn mess given all of the potential conflicts and combatants still on the chessboard that don’t even have to involve Dany — the WW’s, Euron Greyjoy, Littlefinger, mad Queen Cersei and Dorne/Tyrell coming after Cersei. Her job will be to rebuild and grow into an actual ruler. She is an ambitious young woman with good intentions to make the world a better place, but still lacks the moral sophistication and maturity to realize that this is not achieved by dramatic military victories and conquest, but by the unglamorous daily march of solid and responsible decisions on tough and thorny problems that are grey, not black/white. Growing into this realization is where the plot is taking her, not some grand military victory