Trainer customization has been around since Generation VI of Pokémon X & Y, and it’s been confirmed that the feature will continue in the eighth generation with Pokémon Sword & Shield. [Thanks, Serebii.]
The confirmation comes from a Uniqlo and Pokémon collaboration for a Pokémon-themed T-shirt design contest. Its winner was revealed with the above Gyarados and Magikarps T-shirt, which fans will get to purchase from Uniqlo. Additionally, it’s been revealed that the T-shirt will be available in Pokémon Sword & Shield as a Trainer customization item, confirming the feature for the game.
Furthermore, the next issue of CoroCoro magazine which releases on June 21 will include more info on Pokémon Sword & Shield. However, considering that it is releasing shortly after E3 2019, it might be similar info or a follow-up.
Pokémon Sword & Shield releases in late 2019 for Nintendo Switch.