Ever since news for this game began in earnest I've been maintaining a google doc tracking the Pokemon that have Megas, sorted together by region and Pokedex number. If this alleged list of DLC Megas winds up being accurate, we now have...
Kanto, Johto, Hoenn
Sinnoh through Paldea
Falinks and the 4 Paldea lines are together to stay on one page in the google doc. I also included Hoopa despite no game data hinting at it due to its status as a DLC mascot making a Mega likely. In addition, Groudon and Kyogre are being counted as Mega-adjacents despite their forms being named and working a bit differently.
This leaves us with 90 Mega Evolution users and 96 Mega Evolutions in total.
Sinnoh through Paldea
Falinks and the 4 Paldea lines are together to stay on one page in the google doc. I also included Hoopa despite no game data hinting at it due to its status as a DLC mascot making a Mega likely. In addition, Groudon and Kyogre are being counted as Mega-adjacents despite their forms being named and working a bit differently.
This leaves us with 90 Mega Evolution users and 96 Mega Evolutions in total.