I think it remains to be seen whether the people of Meereen are going to be better off with a dragon queen than those of Astapor were without one. I don't care whether Daenerys ever goes to Westeros, actually, provided her story is interesting wherever it takes her, as (for me) the Slaver's Bay arc has been. I think it was a mistake for her to stay in Meereen because she doesn't have the right temperament to rule there well. Even the minimal concessions she's willing to make to the customs of her new subjects are so upsetting that she can't take the steps that would be needed to actually secure her throne. The culture of Meereen bothers her so much that all she wants to do is fix it, but as Barristan says in one of his few moments of insight and candor, you can't force people to be better (by your alien social ideals) than they are. One of the going fan theories is that Jon will die and be resurrected (probably by Melisandre, in the same manner Thoros resurrected Beric), and that with his "death" his watch will end and he'll be released from his vows. I don't like the idea, but I wouldn't rule it out as an argument someone in the text might make.