So we've had quite a number of ORAS Mega reveals and it's pretty obvious they're going to try spread representatives for each elemental type.

So far confirmed Mega's:-
Sceptile - Dragon/Grass
Swampert - Ground/Water
Blaziken - Fire/Fighting
Slowbro - Water/Psychic
Lati@s - Psychic/Dragon (Never officially revealed as X/Y Megas so safe to call them ORAS mons)
Altaria - Dragon/Fairy
Lopunny - Normal/Fighting
Audino - Normal/Fairy
Sableye - Ghost/Dark
Salamence - Dragon/Flying
Metagross - Steel/Psychic
Diancie - Rock/Fairy
Groudon - Fire/Ground
Kyogre - Water

Tallying that up it means these are represented.

Dragon x4
Psychic x4
Fairy x3
Normal x2
Ground x2
Water x2
Fire x2
Steel x1
Rock x1
Grass x1
Dark x1
Ghost x1
Fighting x1
Bug x0
Ice x0
Elec x0
Poison x0

So basically the likelihood is the next revealed Megas will be anything from a combination of Steel, Rock, Grass, Dark, Ghost, Fighting and near guaranteed is there being a Poison, Elec, Ice or Bug.

What do you think is most likely going to get a Mega with the types left behind just picking from the leftover types?

>Pic related as one of the most unlikely to get Mega