Also, Daenerys is now in charge of the Dothraki, a people who think that salt water is poison because horses can't drink it and won't cross the sea. That has to be setting us up for a Narrow Sea crossing, right? The Dothraki and the Ironborn are much more alike than one might think, considering they earn respect by taking things (e.g., horses, ships, lives) from weaker individuals and are generally just into taking the piss out of everyone.
A combination Dothraki-Ironborn army is a scary prospect to think about, and seeing a bunch of Dothraki horse lords riding their steeds off of Ironborn ships, possibly with their long braids intertwined with seaweed, would likely cause every lord in Westeros to send out all their emergency ravens simultaneously, thus clogging the raven airways, and causing a massive raven outage. And this is before they see Dany's dragons.