In one way or another it’ll end up being Dragon Ex Machina. Either Daenerys takes King’s Landing with her’s or the White Walkers murder them all with theirs. One way or another I think the ending is likely to end up too rushed to be heavily climactic. Mind you all 7 episodes are slated to be near feature length so that works out to somewhere around 10.5 hours which is nearly the Length of the original LOTR trilogy. I guess that does offer time for a lot to happen but still. Like you said the build up will always be better than the payoff unfortunately. Especially in a show like this. One side or the other HAS to win, that’s just what needs to happen. So that means either everyone gets wiped out by the Walkers, Daenerys kicks major ass, or Cercei fucks them all over and stays in power. As far as I’m concerned there are no other options, at least as things stand right now.
What I will say, it’s gonna be a damn long wait. I too binged the entire 7 seasons during the run of just season 7 so I’m not used to having to wait for more GoT. This is going to be a torturous wait.