With the release of the Galar birds and the last missing Genesect form, here are all the remaining unreleased Pokémon from generations 3 through 6 including the last Galarian Forms and evolution. :
Pokémon Sword and Shield Galarian Pokémon Form list, including Galarian Weezing, Galarian Zigzagoon and other Galar Pokémon | Eurogamer.net
Galar Pokémon Assets Added to Pokémon GO | Pokémon GO Hub
List of Galarian Forms | Pokemon Sword and Shield|Game8
Pokemon That Need Regional Forms or Evolutions in a Pokemon Legends Galar Game
Pokémon Go Galarian Pokémon forms list | Eurogamer.net