So, Daario tells Daenerys that she will need 1,000 ships to take her Dothraki horde across the Narrow sea.
Meanwhile, Theon and Yara steal 1,000 ships from Euron at the Iron Islands and are headed to strike a deal with Daenerys in Mereen.
Both groups used the phrase "a thousand ships" specifically, so it seems likely that they will be attempting to team up once (if) they reach Mereen. That seems like a very odd grouping, though - the Greyjoys and Daenerys.
I'm also really interested to see where the Hound's story takes him. The guy said "the gods have kept you alive for a reason," which is obviously a pretty big hint in this franchise that he's going to have a pretty major role the rest of the way. The Brotherhood without Banners doesn't seem like a big enough storyline for him to be involved in. I'm guessing it will involve Arya, Brienne, or the Mountain.