Splatoon 3 was announced during the latest Nintendo Direct scheduled to release in 2022.
“Splatoon 3 arrives on Nintendo Switch in 2022! In the wake of chaos, enter the sun scorched Splatlands and the new city, Splatsville, inhabited by battle-hardened Inklings and Octolings. New weapons, moves, and more await, so be sure to keep an eye out for updates in the future.”