Bran becoming King. Makes sense if planned out by Bloodraven. He's been slowly moving things around and controlling the fates of others to ensure he is in control when the white walkers attack. (It's possible it will be more of a dictator situation rather than king, or he will control/heavily advise whomever is the "king")
Dany going "mad". (f)Aegon is a huge problem for her conquest. She has been told her whole life she is meant to save Westeros. She has put in all the time and effort. She has dragons. But is she a savior or a conqueror?
Jon ultimately killing Dany. A lot will change in the lead up, but it probably roughly plays our similarly.
Varys killed by Dany. I assume related to the (f)Aegon plot. He isn't going to join Dany in Essos. He'll just be on the wrong side of things.

There is plenty more. The issue of course is that you need A LOT more story you need to tell. And the books have a lot more characters. And we need to rewind a handful of stories that show already closed off much earlier. So I understand that there is a lot to write. But also, I agree it's been soooooo long.