Additionally, many references to "surrounding regions" are present within X and Y's storyline, mainly in how Kalos was one of the many regions that took part in the war. Many. Regions. REGIONS. As in more than one that surround the Kalos region.
There's also a reference to new regions REGIONS in the X and Y strategy guide, where it states that "fourteen berries can only be obtained via trade from other regions." REGIONS.
Additionally, the giant man in Pokemon X and Y is called AZ. A, in Greek, is Alpha. Z, in Greek, is Omega. What does this mean?
Anyway, back to the point about A being Alpha and Z being Omega. Arceus has never been released officially before. Zygarde has had nothing significant happen to it except that it randomly shows up in Terminus Cave after you have defeated the Elite Four. Zygarde is the third of a trio of legendaries, and Arceus created the Pokemon world, while also having a name that starts with an A. Zygarde starts with a Z. A. Z. AZ. XY.
Arceus would represent the Alpha of the duo - the creator, the one that started it all. Zygarde, on the other hand? Zygarde represents a snake-like thing. In the Bible, the devil takes the form of a snake. Could Zygarde's "secret power" possibly be the Pokemon equivalent of the devil, representing the end, while Arceus represents the beginning?
Could Arceus and Zygarde each be the legendaries of future 6th Generation Pokemon games, each of them occupying their own region? Time will only tell. But it's an interesting prospect.