Nintendo announced Splatoon 3 at the end of the February 2021 Nintendo Direct. Things kicked off by showing characters customizing their character. (You even get a Salmonid friend.) Then, it showed them heading to the city. It will appear on the system in 2022.
This comes after quite a bit of teasing. For example, in 2020 Nintendo hinted the game was in development. In a New Year’s Message, there was an “SOS” message. If people looked in the waves, they could see the note, “Save our Salmons.” The salmons seemed to refer to the Salmonid characters that people face in the Salmon Run Splatoon 2 mode in the name of gathering eggs for Grizzco Industries.
Splatoon 2 is in development for the Nintendo Switch and will debut in 2022.