Ever since James Gunn was rehired as the director for Guardians of the Galaxy Vol. 3, its production start was always questioned by fans. This is especially true after Gunn was hired to direct The Suicide Squad shortly before he was rehired, which would end up ultimately delaying the MCU film's release even more. However, Gunn has been insistent that his involvement with Warner Bros. hadn't affected the new production start for Guardians of the Galaxy Vol. 3.
Not even the recent pandemic had any affect on it.
So, when James Gunn announced that he was working on another project for Warner Bros. in the form of a television show, fans become concerned again, but Gunn quickly dispelled any thoughts of delay with Guardians of the Galaxy Vol. 3.
The goal is to have Peacemaker go into production in early 2021, prior to Gunn beginning work on rival Marvel Studio’s third Guardians of the Galaxy movie.
This implies that filming for Guardians of the Galaxy Vol. 3 won't begin until at least mid-way into 2021 after filming for Peacemaker has finished, since Gunn himself was reported to be directing several episodes, too.
When this news was brought up to James Gunn on Twitter, he replied with two clarifying tweets regarding the production of Guardians of the Galaxy Vol. 3 and whether Peacemaker would conflict with it:
In the past, James Gunn said that he wouldn't begin working on Guardians of the Galaxy Vol. 3 until after The Suicide Squad was finished, which could end up being right up to its release in August 2021.
In his second tweet, Gunn reaffirms that the production start date for Guardians of the Galaxy Vol. 3 has not changed, despite this new commitment and the ongoing pandemic.
WHAT THIS MEANS
Since James Gunn will only be directing several episodes of this limited Peacemaker series and production for it would begin "in early 2021," then it would not affect what he has said in the past regarding both The Suicide Squad and Guardians of the Galaxy Vol. 3. Something interesting that Gunn does say is that "Normally I would have been taking more of a break in this space," indicating that his work on The Suicide Squad may, in fact, already be done.
It is still confusing when exactly James Gunn plans on starting production for Guardians of the Galaxy Vol. 3 since Gunn hasn't given his own definition of when The Suicide Squad for him would be "done." This could mean either finishing the editing or making sure everything is fine right up until its release.
So, it's possible that after Gunn has finished directing his episodes of Peacemaker in early 2021, he may finally move onto Guardians of the Galaxy Vol. 3 in Fall 2021 or possibly a bit earlier than that.