Speaking as someone who's never read the novels, never seen the television adaptations, and has no intention of ever doing either*, it's completely obvious how the series is supposed to end, right? Like, the whole premise is that, on the one hand, it's an exploration of the brutal realities of naked power politics, where idealistic heroism and chivalric principles matter much less than Machiavellian cunning and ruthlessness; and on the other hand, relentlessly cold and inimical Others lurk in the background, kept away from civilization only by works wrought through ancient practices no one understands any longer, and the continued efforts of small numbers of valiant men; and also it's an almost comically long and digressive series.
So obviously, obviously, the way it ends is that all the heroic and self-sacrificial characters get taken out one by one by the various rat bastards, and then the rat bastards all stab each other in the back over the course of a self-indulgent half-a-million words or so, until some random rat bastard or other rises to the top of the heap and becomes undisputed King of the Realm, and this takes so long that both characters and readers almost forget about the genuine threat of the relentlessly cold and inimical Others lurking in the background, kept away from civilization by etc. Who are now no longer kept at by by the self-sacrificial efforts of small numbers of valiant men (all of said men having since been brutally murdered by the rat bastards), and who proceed to sweep over the land annihilating everything and everyone and rendering all the efforts of the various rat bastards to achieve their overweening ambitions useless and hollow.
And whether you choose to view this as an environmentalist allegory for climate change, or an atheist's defense of rectitude and morality in the face of nihilism, or a fatalistic reflection upon death as the inevitable conclusion of all life no matter how long and vividly lived, or an appropriately medieval warning upon the vanity of ambition**, it's a thematically rich ending, and one that actually retroactively justifies the length of the stories, as their excessive detail serves to show how easy it was to forget the whole "impending doom" thing.
Like, it's obvious, right? And, I mean, what little I have read of Martin's other works indicates that he's a fine writer of Weird Tales with a lot of knowledge of that genre, and so writing what is essentially a decent Clark Ashton Smith story expanded into the world's longest shaggy dog joke seems actually entirely in character for the man.
Am I crazy, have I wildly misinterpreted the dim rumors of the plot that I've received at second, third and fourth hand, or is this an unoriginal thought that at least twenty other people have had before me?