>>20487208X/Y's Megas seemed to have a nice pattern to me.
Gen I representation:
Venusaur, Charizard, Blastoise
Alakazam, Gengar
Kangaskhan
Gyarados
Pinsir (Heracross conterpart)
Aerodactyl (fossil)
Mewtwo
Gen II representation:
Heracross (Pinsir counterpart)
Ampharos
Scizor
Houndoom
Tyranitar (pseudo)
Gen III representation, and so forth:
Blaziken (ORAS teaser)
Gardevoir
Mawile (ORAS teaser)
Aggron
Medicham, Manectric (these two are next to each other in the Pokedex, but I don't think they're related right?)
Banette
Absol
Garchomp
Lucario (will NEVER EVER be a legendary representation)
Abomasnow
OR/AS I believe will do something similar. What we have so far:
Sceptile, Swampert (starters)
Sabeleye (Mawile counterpart)
Altaria
Salamence, Metagross (pseudos)
Latias, Latios (legendaries)
Slowbro (Gen 1 representation)
Lopunny (Gen 4 representation)
Audino (Gen 5 representation)
Diancie (Gen 6 representation)
This makes me personally believe that OR/AS will add:
another Generation I Mega
two Generation II Megas
another Generation IV Mega
another Generation V Mega
another Generation VI Mega
My guesses:
Mega Golduck
Mega Steelix, Mega Kingdra, or Mega Azumarill
Mega Gallade, or Mega Slaking, or even Mega Camerupt
Mega Dusknoir, or Mega Rhyperior
Mega Archeops or Mega Zoroark
Mega Noivern
I'm guessing the following will NOT get Megas in OR/AS, and instead will be postponed to the next Gen I remake:
Dragonite, Machamp, Poliwrath/Politoed
Just my patternfag opinions.