>>58035660All Pokรฉmon that can Mega Evolve can be found in Kalos, regardless if the Mega comes from XY or ORAS. There's a few exceptions, namely the Hoenn starters, the Eon duo, the weather trio and surprisingly, the Buneary line. Lopunny was confirmed for Z-A in the latest trailer which means the only Megas with serious risk of not appearing are ones that are very tied to Hoenn. They have to figure out a way to gift their Mega Stones in some game and Torchic was originally in XY as a bonus so I'm pretty confident these are going to be in too. Evelyn and Dana use Latios and Latias respectively so if they get to appear, then these two might as well.