Any chance that George will only have part of the Dothraki forces that will unite under Dany actually cross the narrow sea? What about none of them at all? Somebody like Tyrion or Barristan or Marwyn (or of course, Missandei) could dissuade her with the cultural and logistical challenges. Plus, that Volantis will likely be attacked by them, the likes of Qohor (especially, given the Three Thousand), Myr, Norvos, and Pentos could be threatened.