Galarian Form distribution prior to update:
5 Kanto origin families, 6 Pokemon
1 Johto origin family, 1 Pokemon
1 Hoenn origin family, 2 Pokemon
3 Unova origin families, 4 Pokemon
Galarian Form distribution after update (currently known):
8 Kanto origin families, 10 Pokemon [+3/+4]
1 Johto origin family, 2 Pokemon [+0/+1]
1 Hoenn origin family, 2 Pokemon [+0/+0]
3 Unova origin families, 4 Pokemon [+0/+0]
Gigantamax distribution prior to update:
10 Kanto Pokemon
1 Unova Pokemon
1 GO(???) Pokemon (currently unavailable)
14 Galar Pokemon (1 currently unavailable)
Gigantamax distribution after update (currently known):
12 Kanto Pokemon [+2]
1 Unova Pokemon [+0]
1 GO(???) Pokemon [+0]
18 (19) Galar Pokemon (Urshifu has two forms)[+4 (5)]
These numbers may change as we get more information about the DLC, but right now Kanto and Galar are increasing their already significant lead in regional/gigantamax form distribution.
E: might as well do this as well
Currently confirmed returning Pokemon by region (as shown in the released infographics):
11 Kanto (Horsea, Seadra, Chansey, Magnemite, Magneton, NidoranM, Nidorino, Nidoking, Zubat, Golbat, Electabuzz)
6 Johto (Kingdra, Blissey, Crobat, Elekid, Marill, Azumarill)
7 Hoenn (Azurill, Beldum, Metang, Metagross, Spheal, Sealeo, Walrein)
6 Sinnoh (Magnezone, Happiny, Gible, Gabite, Garchomp, Electivire)
5 Unova (Zorua, Zoroark, Larvesta, Volcarona, Cryogonal)
3 Kalos (Dedenne, Amarua, Aurorus)
2 Alola (Rockruff, Lycanroc)
If we include the "obvious counterparts" which are currently unconfirmed, the numbers are as follows (counterparts added in parentheses):
15 Kanto (NidoranF, Nidorina, Nidoqueen, Magmar) [+4]
7 Johto (Magby) [+1]
7 Hoenn [+0]
7 Sinnoh (Magmortar) [+1]
5 Unova [+0]
5 Kalos (Tyrunt, Tyrantrum) [+2]
2 Alola [+0]
Jynx was not included as it is no longer an "obvious counterpart" to Magmar and Elekid.
Legendary Pokemon were not included as we don't have a confirmation of which will be returning, they will obviously increase these numbers. Similarly, Kanto Slowpoke, Slowbro, Articuno, Zapdos, Moltres, and Johto Slowking were not counted because iunno i felt like it. Oh also I didn't do the ones already known to be programmed into the game (like Bulbasaur and Squirtle) because we knew about those months ago and they'll likely be releasing with Home, not with the DLC.