I'd love to see a Kroot Mercs release; always loved their look.
To me, they have a vibe similar to the Na'vi from the Avatar movie. Ideally, I'd love to see them get a pterodactyl-like flyer/FMC, with a couple of Kroot manning a giant crossbow in a howdah on the beast's back. Or a Kroot HQ character riding a monster similar to the Lizardmen carnosaur, or a big, six-legged lizard-panther or something. I doubt we'll get anything that epic, as GW seems to keep these supplemental releases fairly tame.
I'm just hopeful the Kroot would get an HQ, as the Harlies dex has me concerned that they might not.
Also still crossing my fingers for Thousand Sons, DE Wych Cults, and Deathwatch supplements...