There are some Pokemon that seem to frequently receive extra love in the card game (like Malamar, Empoleon, Bronzong, Donphan, Exeggutor, etc.) - so I would say one of those will probably be upcoming (along with some of those seen in the votes).
I would like to see some of the very rarely used/underwhelming 'mon with BREAK evolutions, like Furret, Ledian, Swootbat, Arbok, Dodrio, Hypno, Walrein, Escavalier, Mandibuzz (I miss you!) etc., etc. I also think it would be cool to have a Fossil themed set (yes, I know this was done before and I was actually playing when it was released) with BREAK evolutions for some of those we haven't seen in a while, like Omastar, Kabutops, Bastiodon, Rampardos, etc.
But really, as long as they keep making them, I'll be excited (just like Ancient Traits, Plasma/Rocket/Gym Leader Pokemon, Legends, etc.)