It will probably be a ORAS event, not XY. I doubt that the event will be in 2015. To be honest my guess would be it will probably be the first or second event within ORAS. And why does everyone expect a Pokemon Z version? They dont always make a third game. If anything Sigma Emerald would be thought of first. I honestly dont see Pokemon Z ever happening otherwise they would have already made it instead of ORAS. Anyways back to the subject Hoopa and Volcanion will more then likly be ORAS exclusive with the ability to move them between the XY and ORAS as speculated with all the other pokes and events.
Lol, none of that makes any sense in regards to justifiying no Pokemon Z:
1) Yes, they've ALWAYS made a 3rd version, and in the case of Black and White, they made a 3rd AND 4th version (Black 2, White 2)
2) Why would they make an Emerald remake? THAT'S where they've never done a third game in the series: The remakes of Fire Red and Leaf Green never had a Yellow version, the remakes of Heart Gold and Soul Silver never had a Crystal remake.
3) WHY would they have made Pokemon Z already? Pokemon Ruby and Sapphire came out, THEN Fire Red and leaf Green THEN Emerald. They didn't release Emerald before the remakes, so why would they release Z before teh remakes now?
4) Remember all the people that said there were clues for the Hoeen remakes and everyone ridiculed and dismissed their claims until they actually WERE announced?
5) They wouldn't have called the games X and Y if there was going to be no Z, otherwise the games would have been called Y and Z. Contrary to what people think, they don't just wake up one weekend and bang out a full pokemon game and ship it out monday, the games take a VERY long time before they're made, and they plan quite a long time in advance before they make the games, so they knew exactly what games they were going to be making before they even announced publicly when X and Y were coming out. X and Y were announced a year before it hit store shelves, Smash Brothers same deal, especially when all the pokemon games in a given generation need to be compatible with each other, they all need to be planned out to ensure compatibility. Why else would the mega evolved versions of Latios and Latias be in the current games' programming if they hadn't already planned them long before the ORAS remakes were ever announced?