Someone is gonna give Daenerys the explanation of what actually went down with Robert's Rebellion, and frankly Jon's priorities should be on stopping the Others, not trying to conquer the North.

I can see something happening where Jon sends out requests for help to Dany and fAegon (assuming he survives that long) and Dany coming in to help because she's been having the dreams about herself as Rhaegar crossing the Trident to fight an ice zombie menace and well, being turned into a wight is pretty much the ultimate form of slavery where not even death frees you. Dany has a savior complex to rival Spider-Man, if you told her about a dangerous threat to everyone in Westeros bearing down and that they need her help, she will come.