These are all the kanto mons that are returning(considering the new list of not returning mons) in dlcs but that we haven't seen in trailers/arts. This mons COULD potentialy get a new galarian form.

Weedle
Kakuna
Beedrill
Spearow
Fearow
Ekans
Arbok
Jigglypuff
Wigglytuff
Venonat
Venomoth
Psyduck
Golduck
Mankey
Primeape
Abra
Kadabra
Alakazam
Bellsprout
Weepinbell
Victreebel
Tentacool
Tentacruel
Doduo
Dodrio
Seel
Dewgong
Drowzee
Hypno
Voltorb
Electrode
Jynx
Pinsir
Dratini
Dragonair
Dragonite

I didn't write kantonian fossils and the mons that already have an alolan form.
Next time i'll post next gens.