The Official website of the anime of Pokémon have announced that the newest season of this series will be called XY & Z.
The Website describes the story as follows:
What secret is hidden in the legendary never-before-seen pokémon Zygarde? What is the mysterious phenomenon that occurs only with Satoshi’s (Ash’s) Gekkōga (Greninja)? What is the aim of Alain and Team Flare, who stands in the way of Satoshi and his friends? When all the mysteries are revealed, the greatest danger the Kalos region has ever seen will appear!