So, it looks like we have compatibility notes for how this is going to work and it seems to be as we feared. New moves/abilities/Megas introduced in OR/AS cannot be used in battle against players using X/Y. Here is the write up on Serebii about it.
"Online and wireless battles in the games remains exactly the same as before. While between Pokémon Omega Ruby & Alpha Sapphire games you can do and use anything, when you connect with players of Pokémon X & Y, there are several restrictions. Essentially, you cannot use any of the new Mega Evolutions, new moves and new abilities in battle against these players. The game will inform you as you select your team whether or not it can be used.
The Battle Spot changes this up somewhat. In Free Battle, Pokémon X & Y and Pokémon Omega Ruby & Alpha Sapphire run different matchmaking schemes so they will never encounter each other. In Rating Battle, they also run different schemes, with Pokémon Omega Ruby & Alpha Sapphire's scheme changing somewhat from the standard of Pokémon X & Y
ΩR/αS League: Open only for players of Pokémon Omega Ruby & Alpha Sapphire. This league lets you only use Pokémon that were caught, hatched or distributed in Pokémon X, Y, Omega Ruby & Alpha Sapphire.
XY League: Open only for players of Pokémon X & Y. This league lets you only use any Pokémon, including those that were transferred from Pokémon Black, White, Black 2 or White 2."
This link contains the above and a chart illustrating it and trade info as well.
http://serebii.net/omegarubyalphasapphi ... lity.shtmlSo, it looks like a decision will have to be made to either require OR/AS or have Gym Leaders have the capability to have X/Y compatible teams.
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