NHK is listing in its “Changes in Domestic Programs in the Second Half of 2020” document that the Attack on Titan The Final Season anime will premiere on December 7, 2020.
A special preview video after the final episode of the third season had announced in June 2019 that the final season would premiere in Fall 2020. However, the anime’s official website and videos do not list a specific premiere season, but list only that the show will air on NHK-General.
FUNimation Entertainment and Crunchyroll had previously announced that they will stream the anime with English subtitles, and FUNimation will additionally stream the anime with an English dub. Crunchyroll will stream the anime in the United States, Canada, the United Kingdom, Ireland, South Africa, Australia, New Zealand, Iceland, Sweden, Norway, Denmark, Finland, the Netherlands, and Latin America.