I'm not even sure Ash will capture anything... the early tone set thus far anyway gives that impression.
In that case Ash better bring his Kanto-Alola Teams back because the idea of his only Pokemon through this entire series being Pikachu already sounds unappealing.
Ash's Possible Galar Team
The Usual Suspects (aside from Fire which I think is being skipped like Grass and Water were)
-the primary-
Grookey or Applin (the Grass Starter or alternate Grass type)
Sobble or Chewtle (the Water Starter or alternate Water Type)
Rookidee (the Regional Bird)
-the secondary-
Dreepy (the Gible or Goomy of the region)
Blipbug or Snom (the Bug Type)
Clobbopus or Farfetch’d (the Fighting Type)
Silicobra (the Ground Type)
-the tertiary-(the unlikely, but might be cool to see)
Zigzagoon: Dark/Normal-all of Ash's Dark types have been dual types with an anti-hero design to them (ninja, heel wrestler, delinquent). I think Obstagoon might qualify, but I'm not sure. Not helped by the fact it is Team Yell's leader's Signature Mon.
Toxel: It'd be the logical progression of Naganadel. A Poison type that can use an Electric attack to a Poison/Electric type, but well you know there is still Pikachu to consider here. Would they really go that extra step and give Ash a second Electric type?
Ponyta: If he doesn't get Blipbug it would get him a Psychic (and upon evolution)/Fairy type. Also the "Ash is a Brony" memes would be funny. Plus the Ponyta line was like the only Kanto Pokemon that Ash bonded with but did not catch so it might be a nice call back to that.