>tl;dr If Z is real, would it contain all legendaries, and pokemon and mega stone exclusives?

So, i want to catch 'em all right. or as many as i can within the latest pokemans.

I have X and im wondering should I buy Y? or should i wait to see if there is a Z? Would Z contain all the pokemon, like both X and Y exclusives? and also would you be able to get Yveltal and Xerneas in Z? Aswell as getting the mega stone exclusives from each game?

Or would it be best just to spend a bit of money on Y then get Z when/if it comes out. money isnt exactly a problem for me, so i could get all of them but of course spending less is always best.

If anyone knows any rumors or has any thoughts of their own, feel free to share.