Ash's Snorlax probably returns.
Serena's Fennekin, Clemont's Luxio and Jessie's Pumpkaboo evolve.
A Florges (probably Ash), a Noibat (probably Clemont) and a Gothita (probably Serena) will join the party.
XY055/XY056 show a Goomy joining Bonnie but it seems it won't be caught.
An Avalugg is also shown but only on one poster, the others don't have it.