Entirely possible/probable - I knew the first episode was going to be moving everyone to where they needed to be before hell is unleashed. But not everyone is in place, so likely you are correct But a significant part of the fun with GoT is wild speculation, and I am thoroughly content with being wrong
DS says he thinks the frozen zombie king is the antecedent of whatever it is John Snow is the 6th of. As you can see, I haven’t followed the show, missed a few seasons, don’t know who most of them are or how they’re related to one another, but I thought the red-haired Stark girl was married to Peter Dinklage at one point. On the show, not in real life.
Tyrion (Peter Dinklage) and Sansa (red head girl) were forced to marry against both of their wills back in season 3 (or early season 4) but the marriage was never consumated as Tyrion refused to force himself on a young girl.
There are lots of theories about who and what the Night King is, largely based on stuff from the books thats barely been touched in the show. The two most likely theories are that he is an ancestor of the Starks or he’s Bran.
The first theory goes that long ago a Stark ancestor somehow became the Night King and whats actually happening now is that the white walkers are coming to help the Starks as their activity has bumped up the more the Starks are in trouble. There is a lot more to it than this obviously.
The second is that at some point in the future Bran will warg himself back in time, much like he did with Hodor, trying to stop the formation of the white walkers but somehow screws up and gets stuck in the Night Kings body and gradually goes insane.
Everything that has happened in the last two seasons (three counting this one) is based on the outline that Martin gave them. Martin is on record as saying that the ending of the series is the same as the ending he plans for the books. I’d call that canon. Martin says the only differences that matter will be for some secondary characters but for the main outcomes its going to be the same.
And since the TV show is the ONLY ending we’ll ever get since Martin is never going to finish the books it the only canon we will ever have.