According to reliable Pokemon news site Serebii, there will be plenty of Pokemon appearing in new Gigantamax forms over the coming month as part of the Gigantamax Festival.
Update 4/6/20: This information has been confirmed, so expect the following Pokemon!
Pokemon Sword Gigantamax Pokemon
- Toxtricity (Ampled Form)
Pokemon Shield Gigantamax Pokemon
- Toxtricity (Low Key Form)
Head into the Max Raid Battle Event as of 1 pm today to be able to encounter these versions of Pokemon. You have until 11:59 pm on June 29 to catch them all.