I figured it out. Before anyone else.
bran is going to discover he can communicate with the past, the dead, in his visions.
they'll relive all these moments we've heard about, they'll show us jon snow is offspring of lyanna and the mad king, he's the fire/ice that is the whole show focus. massive war against the white walkers, etc, it'll be cool.
Anyway - - -
Bran will discover he can speak with the dead. He'll tell a younger ned stark to do something differently - likely, step up to the throne and take it, instead of letting robert baratheon do it.
the series will END with the entire stark family - alive and happy - living in this alternate universe. They're running a beautiful kingdom, just and fair. we'll catch glimpses of what could have been, which is the new reality. Cersei and Jaime will be happy farmers. Tyrion will be married to shae with lots of babies. All those funny outcomes, where these people should have ended up.
They do everything else with this show - resurrections, dragons, etc... a little time travel communication to make Westeros the place it should have been = the happy ending that fans will love.
Nobody's shared this theory. But I think this is how the show ends in a 2 or 3 years. We fall in love with all these characters, sad to see them perish... and in the end, they all have a new life and they're all living and happy, and the fans get their favorite characters to have a happy ending.