Kalos was a bit too recent to get regional forms in 2016 and 2019, but 2022 will mean it's been 9 years since Kalos and Galar was okay with regional variants of Pokémon introduced in Unova 9 years ago. I would love Hisuian forms for Pyroar, Furfrou, Gogoat, and Avalugg, but feel they'd probably only do two lines. Maybe Clawitzer and Gogoat due to mono-typings and little notability?
Water could go to one of the land-dwelling aquatic mons like Hippopotas or Garchomp deciding to return to the sea, Flying to something like a lighter Dodrio or origami Porygon, Normal to maybe a Poison-, Dark-, or Steel-type mammal Pokémon like Sneasel or the Nidorans mellowing out and becoming more natural, Grass to a modern Steel-type's primitive ancestors like a wooden Voltorb or Forretress, and Bug to an already insectoid 'mon like Drapion or Lurantis.