If Jon survives the stabbing (I really hope he does !) then he could play apart, or else all the above theories will be invalid.
- fAegon will rule Westeros for a while, then Dany will defeat him, in a second dance of dragons. But the people will hate her because they believe fAegon to be the real king. She will grow mad and become a Tyrant. I dont see Jon killing her. Because in the books, their story is far, far away from each other. I think she will actually rule a little while longer but will eventually be killed.
- Bran won’t become king, because he is the Three Eyed Raven. Maybe he wont even return from behind the wall ?
- Rickon will be Lord of Winterfell.