The official anime website of Demon Slayer: Kimetsu no Yaiba announced that the the sequel of the series with a subtitle “Entertainment District Arc” will premiere this October 2021. The said sequel will split into 2 cours that will air this Fall 2021 and Winter 2022.

Other details on the sequel of Demon Slayer: Kimetsu no Yaiba will be reveal this September 25, Saturday during the airing of the Infinite Train movie which will be airing for the first time on Japanese terrestrial television.
Prior to that, it has also been decided to broadcast “Tanjiro Kamado Special Edition” from the 11th in order to deliver the mission that has been challenged as a demon slaughter corps from the beginning of the story of Tanjiro Kamado and others.
Source: ORICON NEWS