All of them are in the list of the most popular Pokemon from each reagion, but not necesarily all the first places. Let's see:
+ Kanto: Gengar (2º), Pikachu (4º), Eevee (5º)
+ Johto: Tyranitar (2º)
+ Hoenn: Blaziken (5º)
+ Sinnoh: Lucario (1º)
+ Unova: Chandelure (1º)
+ Kalos: Greninja (1º)
+ Alola: Mimikyu (1º)
+ Galar: Cinderace (6º), Inteleon (10º), Rillaboom (29º)
Anyway, I believe all these Pokemon could also be future captures in the series because they have been present in merchandise and promotional art of the anime. Like in the original promotional poster of the anime's current season: Piplup and Croagunk, the hugging Dragonite, Gengar, Lucario, Pelipper, Mew, Greninja, Blaziken....
As far as I can tell, this is how I see which trainer will be for each Pokemon:
+ Pikachu: Ash, naturally. Already have it.
+ Gengar: Ash, naturally. He already has it.
+ Lucario: Ash, clearly. It will happen when his Riolu evolves.
+ Greninja: Ash, clearly. I suppose Kalos' crisis will be resolve and Ash's Greninja will return.
+ Tyranitar: Ash, clearly. I still hope it will be his old friend Larvitar, evolved.
+ Rillaboom: Ash. He clearly needs at least one Starter from Galar, and maybe they plan to use it to increase this Pokemon's popularity, by adding it to Ash's team.
+ Blaziken: Ash. Sounds weird, but this Pokemon really suits Ash. Since I don't think Ash will get a Fire Type from Galar, this is the best alternative.
+ Cinderace: Goh, obviously. But it could take a while to evolve.
+ Inteleon: Goh, now that we know he got Sobble. It could take longer than Raboot to evolve.
+ Chandelure: Goh, as I don't see this one fitting Ash's style.
+ Mimikyu: I don't think Ash or Goh will capture one, so I suppose Jessie's one will return. Then again, considering Goh has three Dustox and an Ekans (all of them, old Pokemon of Jessie), MAYBE Goh will capture his own Mimikyu. But I see it very unlikely.
+ Eevee: I'm not sure, honestly. For Goh, he would be obsessed with getting several Eevees and evolving each one into a different form. Maybe Ash, so it can get its Gigantamax form, but I'm not sure about it.