I'd expect Team Rocket's Jessie and James' signature Pokemon to get them.
Giovanni's signature Pokemon would also get one then which would be either Persian (since this is a yellow remake) or Nidoking/Nidoqueen. I'll go with Persian just because of Pokemon Yellow which took a lot of inspiration from the anime. (not sure though since it has an Alolan form.
Beedrill got a mega evolution so you'd expect it's counterpart to get one eventually too.
And lastly of course Lance's signature Pokemon.
If there are going to be any new mega's I could see them adding them to almost all the remaining ones though that don't already have an alolan form or later gen evolution.