The following are my hopes for new Mega Evolutions in Generation VII:
Starters:
Gen II and Gen IV starters.
I am really hoping that they do something similar to what they did in X and Y where they allowed you to choose a Kanto starter, but being Johto starters instead. The reason I want this is because remakes for the first two generations happened prior to the introduction of Mega Evolution, and it would be nice to have them available early on in the game and later gain access to Mega Evolutions for them.
I'd like it if Meganium, Typhlosion and Feraligatr remained pure Grass, Fire and Water for their megas, but if they were each given another type, my hopes would be: Grass/Fairy, Fire/Ground or Rock, and Water/Dark or Dragon.
As for Gen IV starters, my hopes for these stem from my hope for Gen IV remakes, but we shall see.
Counterparts:
By counterparts I mean the counterparts of Pokémon that currently have Mega Evolutions. Such as Butterfree. Butterfree has no Mega Evolution, and in the past it has been seen by some people to be a counterpart to Beedrill, who obtained a Mega Evolution in ORAS. The term counterpart is a loose term that I use, I'm not sure if the majority see them this way, but I'm not sure how else to explain it. That being said, the Pokémon I am hoping for that are, in my mind, counterparts arr the following:
Butterfree, hopefully it will be Bug/Psychic
Machamp and Golem, since the other Gen I Pokémon that evolve by trade got Megas last Gen. Or is this Gen? You know what I mean.
Milotic, who in my mind is a counterpart to Gyarados. Maybe pure Water, maybe Water/Fairy or even Water/Dragon?
Dusknoir, though this one is debatable to me since it is in itself an evolution of a second stage Pokémon whereas Banette is not.
Slowking, for Slowbro, similar to Gardevoir and Gallade.
Froslass, who is a Pokémon that I love, and I was a little sad it didn't get a Mega, but again, this ties with my hopes for Gen IV remakes.
Luxray, since Manectric seems like a counterpart to me, maybe not though.
New Mega Forms:
I know Gyarados already has a Mega Evolution, but I really want it to have one where it becomes Water/Dragon. I'm not expecting this, but it's something I'd really like.
Pokémon I just plain hope get Mega Evolutions:
Gen I
Raichu
Wigglytuff
Arcanine
Ninetales
Golduck (Water/Psychic)
Dewgong
Marowak (Maybe Ground/Ghost)
Gen II
Noctowl (Dark/Flying or Psychic/Flying)
Sunflora (Grass/Fire)
Ursaring
Skarmory
Gen III
Tropius
Breloom
Solrock
Lunatone
Gen IV
Staraptor
Bibarel
Floatzel
Ambipom
Skuntank
Electivire
Magmortar
Gen V
Musharna
Zebstrika
Excadrill
Seismitoad
Whimsicott
Lilligant
Galvantula
Braviary
Mandibuzz
Gen VI
Talonflame
Florges
Meowstic (one for each gender)
Hawlucha
This is obviously a huge and ambitious list, but since one can dream, haha. Honestly, if only one of these comes true, I'll be pleased. I love to see what people expect and what people want.