With Casterly Rock’s defenses, the Unsullied should be able to last long enough for Dany and her dragons to come swooping in and save the day. Since Euron doesn’t know about the sewer system, the Unsullied should be able to hold him off in time for some dragon-fueled reinforcements or to prepare a retreat.I think Daenerys is going to attack King's Landing or Jaime's army with dragons and Dothraki. She's done with holding back.
Meanwhile, it’s unclear what Jaime’s army is planning to do or where it’s going to go after plundering Highgarden. Perhaps they’ll team up with Euron to take back Casterly Rock.
There is something in the previews, along with Jon Snow back in the north. Beric Dondarrion lights up his flame sword.