I always liked Sceptile though, from the anime to the first time i picked him in Emerald. Camerupt was an ehhhh Pokemon but I heard he is very useful though so i guess it would be cool to have him mega, I just want them to focus more on the cooler pokemon not ones that get over looked.
Or how about they focus on a wide range of Pokemon to satisfy everyone like they are already doing?
Come on, Kangaskhan, Absol, and Mawile were always overlooked, an they received megas. Garchomp, Gengar, and Blaziken were Pokemon that everyone used and loved and they received Megas. They won't stick to one thing like popularity or overlooked ones.
Also I am predicting these Megas to be revealed in the next few months-
-Sharpedo
-Camerupt
-Official Latias
-Official Latios
-Metagross
-Salamence
-Milotic
-Tropius
Really the last 2 are unlikely, but since Wallace was so huge back in Emerald I thought that they might give Milotic a Mega since she is quite the Popular Pokemon, and everyone is dying for a Mega Tropius, so for all we know they might be making our wishes reality. Although, I think they don't want to many Megas from Hoenn, since they already outdo Kanto's Megas.
I know Matsubasa/ Aogiri have their Key Stones. But I guess they will have a temporary control over Primal Groudon/ Kaiorga at the very final battle.
We already know that the Key Stones don't activate Primal Groudon/Kyogre. Since in the Video it shows them turning into their Primal form, it doesn't show any character using the Key Stone, and since Primal De-Evolution is unrelated to Mega Evolution it is highly unlikely the Key Stone triggers it.
They will most likely have Mega Sharpedo and Mega Camerupt.