Here is my tip
Deny crosses the narrow sea and takes kings landing from the lannisters, she allows Sansa to rule the north because she is Tyrions wife and the iron islands chick keeps the iron islands, and the three of them take on the white walkers
If the dominant fan theory is that Jon is the secret son of Rheagar Targerian, then that means that Dany is his auntie? (maybe, I can't remember the family tree exactly).
Targarians also traditionally marry within the family, so perhaps Jon and Dany get together and that is how the alliance is formed?