To be honest, I can't really predict what Gamefreak is going to do next. My thoughts are quite Farfetch'd (HA), but ok.
I'm gonna call the game "Pokémon XYZ" For now, because I'm not really good at creating names for games.
However, what I am thinking of is a SEQUEL to Pokémon X/Y, which would be kind of like HG/SS - Two Regions. Kalos and Kanto. They have way too many parallels, That CAN'T be a coincedence.
Let me explain how this would work.
Everything would go the same, up to the first, personal meeting with Prof. Sycamore. As soon as you meet him, he tells you about a Man-Made Pokémon, that can create steam and even destroy Mountains with his two strong arms. It seems to be threatening the Kalos and Kanto Regions. Thats all he knows about the Pokémon. (Volcanion)
Later, when you've got arround 4 Badges, you'll meet Shauna again. She will tell you, about Calem and Serena, and how they've destroyed Team Flare, also telling, that Lysandre has mysteriously disappeared that day.
After beating the 8th gym, Something terrible happens.
Volcanion has appeared in Geosenge Town, Trying to get into the basement of Team Flare, and succeeds. Lysandre is still alive, down there. The Ultimate Weapon gave him immortality, so he survived his "Accident", as he calls it.
Afterwards team flare flees to Kanto, youve gotta fight it and volcanion, get the badges of Kanto, etc., etc. I hope you get what I mean!
But this is just a theory.
A GAME THEORY :D