Seraphon wave 2 certainly seems likely. Saurus Guard need new models, and we have already seen plenty of Skinks in warbands and other kits (eg. Slann) that are a brand new style.
I'm hoping they also release a new Eternity Warden and Razordon, since those were unceremoniously cut from the 3rd ed battletome. This could be because they don't want to sell finecast since wave 2 is coming relatively soon, or it could be because they have no intention of ever selling those units again and want to remove all the finecast from their AOS catalogue over the next few years.