Pokemon X dex entry: "When the Kalos region ecosystem falls into disarray, it appears and reveals its 'secret power'."
Pokemon Z was already obvious, but this dex entry all but assures us of it.
What will become of him in the future? Mega evolution? Alternate forme via hold item/key item/in-game event?
As an aside, he should have been a Poison type considering he's a serpent, which would let him not get fucked by Xerneas, thus cementing his position as trio master.
I really like Zygarde, and it sucks to see him left in the dust. For now.