One thing I haven't seen anyone talk about
The starter trio is a shot in the dark, but I highly doubt it'd have any starter from Kanto or Hoenn, since those are Pokémon with Megas. Also don't think Paldea's getting anything yet, it's too early. And of course Kalos is immediately ruled out.
So basically what I'm saying, the starters will likely be a combination of Johto, Sinnoh, Unova, Alola, or Galar. And of course the Legends starters are not gonna be chosen again.
Now who exactly they would choose is not a question I can answer