Some fans have discuss the odds that Dani would either be killed before she ever makes it to the 7 kingdoms, or get there when all hell breaks loose and there would be nothing there for her to rule.
Of course there is the whole 3 heads of the Dragon thing, but that isn't on the show yet. Spoiler: Dani can't win by herself, she can only win with two other leaders fighting with her. Most fans are assuming that John Snow is one of them, and no one can figure out who is the 3rd. It is also not know if they must all be related or not. Many fans assume that they had to be related but GRRM confirmed that he never said they had to be related.
Anyway, that is all Season 7 stuff...