Bands? As in... musical bands? Why would you think that? That sounds like something only a handful of people want. Plus that would be better off as a secondary feature of an expansion pack, rather than having an entire game pack dedicated to it.
And that's the thing that makes it likely
I honestly have no idea about the next GP (and I actually think we'll get a SP next). I read the theory about music as well because a tweet from a few weeks ago hinted at something music-related iirc? And so far we only have guitar, piano, violin and pipe organ. Some more instruments like drums, flute, keyboard piano, bass, saxophone etc could be neat. Not really something I would consider a priority, but I could totally imagine them doing it and dedicating a whole pack to it.
But oh my... Sims MM is so much more! It's gnomes coming to life, quirky NPCs, shady skeleton services, equally sad cousin of Tragic Clown, Flamingo dancers, magic beanstalk, Will's giant sim form, magic duels, magic currency, magician shows, minigolf, scary cart rides, charms, winemaking, dragon pets, fortune telling booth, snake charming, bee hives, gargoyles, donkey heads, death from toadification, child spells, new claire the bear interactions, recipes, baking and more... damn how interesting 18 years old game still is :D
I feel like they always go all out with the very last pack. Makin Magic with TS1, Apartment Life for TS2 (which also have witchcraft and small dogs for some reasons) and Into the Future for TS3 (which has loads of contents).
Nuh they had a royal rumble of supernatural creature votes on Twitter for the past week. It'll be Magic theme packs based on how witches are leading like crazy.
I'd be 100% down for a Witches or Supernatural pack if they re-introduced things that were in Makin' Magic. All those cool spells and mini games, even the roller coasters were super unique. But then again, we can't expect too much in one GP, it is EA after all.