>>28930406no they don't Oras/xy doesn't fit with the other games there were no mention of mega pokemons.Its not a retcon either. In the delta episode we get to know that pokemon world operates on different parallel universes wher ein one mega exists and othe not.
Just because ash grneinja is froma demo doesn't make it non canon since you can play it in the main game which connects anime world to the game world.
