The only Pokémon that have been revealed for Pokémon Sword & Shield are the three starters from the Galar region - Scorbunny the Fire-type Pokémon, Sobble the Water-type Pokémon, and Grookey the Grass-type Pokémon.
The question of what types the final forms of the starters will be has been a popular topic of conversation among Pokémon fans, but a new rumor may have revealed them, as well as a new mechanic known as "Spirit Armor," which may tie into similar rumors about something known as "Armored Evolution" that may be coming to Pokémon Sword & Shield.
According to PokéJungle, Pokémon Sword & Shield will feature a new system called Spirit Armor, which will allow a Pokémon to equip a separate item from their held-item which will be similar to a piece of armor or equipment. There will be variations of Spirit Armor that will be unique to specific Pokémon, which will allow them to take on new forms and types, with Mewtwo being listed as one Pokémon with a unique Spirit Armor, along with the three Galar starter Pokémon.
According to the rumors, the three Galar starter Pokémon will keep their solo typing until their final evolution, but equipping them with Spirit Armor will change their type. Scorbunny's Spirit Armor will transform it into a Fire/Fighting-type Pokémon, Sobble's Spirit Armor will transform it into a Water/Ghost-type Pokémon, while Grookey's Spirit Armor will transform it into a Grass/Fairy-type Pokémon. If these rumors are true, then it will mean that TheGamer's predictions about the final evolutions of each starter Pokémon were correct.
The Spirit Armor mechanic will also be important to the mascot Legendary Pokémon, whose type will be determined by the game it appears in and its Spirit Armor. The Pokémon Sword version of the Legendary Pokémon will be a Dragon/Steel-type Pokémon, while the Pokémon Shield version of the Legendary Pokémon will be an Ice/Steel-type Pokémon.
The rumors also state that Pokémon Sword & Shield will have a connection to Kalos, but the player cannot travel there. The idea of Kalos being important in the game makes sense, as the Galar region is clearly based on Great Britain, while Kalos is based on France, and both countries have a long (and often bloody) history together.
There are a lot of rumors to suggest that Armored Evolutions will be a thing in Pokémon Sword & Shield, but it remains to be seen whether they will be linked to a new kind of held item or not.
Pokémon Sword & Shield are due to be released late 2019.