The OP has information saying that Sora is the first in a line up. That info has been there hours before KH13 quoted that tweet.gsc_enon on Twitter hinted that more KH figures could be on the way. Information is from KH13.
I would love Riku and Kairi to get made next! I think Mickey is inevitable, especially where they already made a Mickey nendoroid and they can just modify the old mold. I'd love Donald and Goofy to get made to go along with him too!