I don't think they will cover that much ground in the amount of episodes that are left. I think Tyrion will outlast them all and I think that alliances are going to be broad and sweeping.
It seems to me like the books and the show are setting up alliances that are going to be more encompassing. It's possible Euron and Dany join forces, not saying they will marry, but could be allied. She might just get Euron to lead a different army back to Westeros and prep the throne will she sits in Mereen maintaining the peace.