Production on Guardians of the Galaxy Vol. 3 may start sometime in 2020 according to a report by The Hollywood Reporter. This means a possible release in 2021 or more likely in 2022.
Production on the movie, which had originally been scheduled for a 2020 release, had been put on hold following the firing of director James Gunn. He later returned to the project, but in the interim had taken on directing DC’s Suicide Squad 2. So work on Guardians of the Galaxy Vol. 3 will need to wait until he has fulfilled his commitment to Suicide Squad 2 (set for an August 6, 2021 release).
Gunn had already worked on the script for Guardians of the Galaxy Vol. 3 but that may need to be altered to accommodate the events of Endgame (won’t spoil that by mentioning possible ramifications) and any other MCU films developed while Guardians of the Galaxy Vol. 3 is in the works.
Could Guardians of the Galaxy Vol. 3 introduce Adam Warlock as teased in the credit scene in Guardians of the Galaxy Vol. 2?