Game Of Thrones: Why THAT Death Was A Mistake (& How It'll Be Different In The Books)
5. Martin's Original Outline

George R.R. Martin always planned for the Others to be the overarching threat of his series, at least in a sense. In his original outline, he wrote:
"The greatest danger of all, however, comes from the north, from the icy wastes beyond the Wall, where half-forgotten demons out of legend, the inhuman others, raise cold legions of the undead and the neverborn and prepare to ride down on the winds of winter to extinguish everything that we would call "life." The only thing that stands between the Seven Kingdoms and an endless night is the Wall, and a handful of men in black called the Night's Watch. Their story will be [sic] heart of my third volume, The Winds of Winter. The final battle will also draw together characters and plot threads left from the first two books and resolve all in one huge climax."
That was written before even the first book had been published, and obviously a hell of a lot has changed since then, including the series expanding from a trilogy into a seven-book series. Nonetheless, it's worth remembering that initial idea for the Others, which is likely to factor in some way into his endgame. The idea of them being "inhuman" likely means we won't see a human being turned into a White Walker like with the Night King (which makes sense, since he himself won't exist). But it also tells us of the broader way of thinking. The game of thrones is a distraction that the humans need to be able to look past, because the Others are coming. It's whether or not these characters, whether 'good' or 'bad', can come together to fight this, and how they scrap over other issues while ignoring the most important one, which is the logical endpoint of Martin's beloved William Faulkner quote that "the human heart in conflict with itself is the only thing worth writing about." In the show, after The Long Night it feels more like the dead were the distraction, with the game of thrones being the real story.
That's not to say there'll be a battle against the others, the humans win, and that's where the story ends. Martin's books are so long, dense, and sprawling that there'll be plenty to resolve after they've gone, and far too anti-war to have a battle be the complete endpoint. But it does suggest that we'll get more than one battle that takes place over a single night, with so many mysteries about the enemy left behind.