With all the expected Megas in the form of Camerupt, Sharpedo etc., Id say it's totally possible that we could actually get more Megas than we did in X/Y, as we have so many at this stage. Does anyone think some Pokemon will get the Charizard/Mewtwo treatment this time? I personally think Blaziken will get a second Mega evo revealed (NOT THAT IT NEEDS ONE) but just to keep it in favour like Swampert and Sceptile.
I don't think we'll get quite as many as we did for X and Y, and I don't think any new megas will get two mega evolutions. As it's been said before, Charizard and Mewtwo had their massive popularity to thank for getting two megas each. I don't think even the most popular Hoenn native pokémon such as Blaziken, Metagross, and Salamence, are quite as possible as Charizard and Mewtwo. There's also the fact that two megas for one pokémon is a bit unnecessary.