Did anyone remember in Emerald when Professor Birch gave you the Johto starters after completing the regional Pokedex? Maybe if they are given in tthis game, they will be holding mega stones similar to the Kanto starters in XY!
To be honest, I would much rather they be saved for pokemon Z/sequels to pokemon X and Y, like instead of the kanto starters we get the johto starters with the mega stones! but that's just wishful thinking. I do however wonder if Maxie and Archie are getting megas, if they do then mega camerupt and mega sharpedo?