If more Megas are implemented, I'd hope that they wouldn't just include Hoenn Pokémon. There are a lot more Pokémon that have been forgotten that could be done justice with a Mega.
For example, Mega Lumineon and Mega Luvdisc, Mega Hitmons and Mega Fossils (not forgotten).
Oh yeah, bring on the MegaDisc! ME ability: Water Veil! Maybe too OP. /sarcasm
Seriously, if they bring on ANY more MEvos it needs to be the other two Hoenn starters, first and foremost. Then they can move on to the nerfed Pokés this gen, like Metagross, Breloom, and Salamence. All three took big hits compared to their previous OU place holdings for the last several gens. Now the fossils, I could get behind that one. Both Cradily and Armaldo have never been ahead of the pack. And while not a fossil Pokémon, Relicanth has always been a hat trick. So any of those could stand the MEvo treatment.
What I REALLY want is the return of diving! That was a very nice addition to the originals and I sorely miss true
diving in the Pokémon World.