I think Jon or Daenerys surviving and getting the iron throne is too much of a cliche for JRRM. But for them to not get it means they'd both have to die. If she's pregnant though then what happens to the kid.
Tyrion and Sansa (if T is a targarean) is a good theory.
Definitely hope Arya and Bran get popped off, both irritating and boring characters, I get that bran is a crucial part of the story but both their story arcs bore me, in both the books and the series.
Jaime and Cersei, one will end up killing the other, my monet is on Jaime killing Cersei (King slayer and all that).
Think Brienne may end up killing Jaime or a big plot twist like that.
Think the hound will kill the mountain as that's good telly, but maybe the hound will die too.
I've got to say... I think they have got a lot to wrap up in one series, I'm not sure how they'll do it.
I can't wait but honestly I will be gutted when it ends.