Most likely 7 kingdoms will separate

Boy is gonna marry Sansa and they'll be Ned x Cat 2.0

^I don't think he'd marry Sansa - they were raised as half-siblings and they are first cousins (assuming that Jon will be revealed to be Lyanna's son in the books too). Even though the books are set in a medieval society where people do marry cousins, I don't think that would happen between such main characters because you have to remember, the books are being read by a 21st century audience for whom cousin incest would also be taboo. The matches between cousins mentioned in the books aren't really portrayed positively.

I like the idea of him being King, but I don't think it'd actually happen. It's too predictable and cliché. I either think he'll refuse the throne or something will happen to make too many people oppose the idea. Or he'll die - again - but I hope not.