They'll be following in the footsteps of last year's Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!, but Nintendo president, Shuntaro Furukawa, has noted a key difference between the two.
His comment below comes from Nintendo's March 2019 Financial Results Briefing, highlighting the fact that the Let's Go titles were developed with the Switch's TV mode in mind, whereas Sword and Shield will emphasise the fun of playing Switch in handheld mode.
These new titles, first announced in a Pokémon Direct in February, have generated a huge response from consumers. Pokémon: Let’s Go, Pikachu! and Pokémon: Let’s Go, Eevee!, which were released in November of last year, are designed to highlight the fun of Nintendo Switch in TV mode, for example by waving the controller at the TV screen to capture Pokémon.
Pokémon Sword and Pokémon Shield are being developed to emphasize the fun of playing Nintendo Switch in handheld mode. We want these games to be played not only by longtime Pokémon fans, but also by consumers whose first encounter with the series was on a dedicated video game platform with Pokémon: Let’s Go, Pikachu! and Pokémon: Let’s Go, Eevee!.