The Flash will be the bridge between the DCEU and the new DC Universe, but James Gunn already revealed that it won't reset the franchise completely from scratch. The birth of a new DC Universe leaves behind the baggage that kept new DC projects from reaching their full potential. In order to ease the audience into it, The Flash will use the concept of the multiverse to rewrite reality and make it possible for a new set of characters to take over. However, this doesn't mean that The Flash will erase the entire DCEU from existence.
The slate for the first chapter of James Gunn and Peter Safran's DC Universe, "Gods and Monsters", includes the DC live-action series Waller, starring Viola Davis as the titular anti-hero Amanda Waller, who she played in the DCEU's Suicide Squad movies. This goes against the idea of a full reboot, as it seems that actors can still reprise their previous roles and possibly retain part of their original backstory. So, even if The Flash reboots the DCEU to give way to the new DC Universe, the return of certain established characters means that the DCEU lives on, only in a different form.
What James Gunn Has Said About The Flash Resetting The DC Universe
DC Studios CEO James Gunn officially announced the official slate for the DC Universe in January 2023. Before revealing the upcoming projects, Gunn expressed his thoughts on the four remaining DCEU movies, Shazam: Fury of the Gods, The Flash, Blue Beetle, and Aquaman and the Lost Kingdom. When talking about The Flash, Gunn said it "resets the entire DC Universe". However, when fans questioned Viola Davis' return as Amanda Waller, Gunn clarified, "The Flash resets many things, not all things. Some characters remain the same, some do not” (via CBR). So, while The Flash will help reboot the franchise, it won't rewrite every single detail from the old DCEU.
The Flash will reset most of the DC continuity and introduce new takes on most characters, but it's still possible for characters like John Cena's Peacemaker and Margot Robbie's Harley Quinn to return alongside Amanda Waller. They technically may not be the exact same versions that debuted in the DCEU, but they're still similar enough to come back in future DC projects without major continuity problems. Perhaps even Jason Momoa's Aquaman and Ezra Miller's Flash will be some of the DC characters who can survive the DCEU reboot with only a few tweaks to their backstory.
The Flash Movie Predates James Gunn's DC Universe Plan
The Flash's multiversal story may seem like a tool specifically designed to justify the change from the DCEU to the new DC Universe, but that was never the case. Development on a Flash movie dates back to the 1980s. By 2017, The Flash was already planned to adapt DC's Flashpoint storyline; and by 2020, the movie's multiversal plot was solidified regardless of the direction that the DCEU would take afterward. It was only after The Flash finished production that the DCEU officially came to an end and plans for the new DC Universe took shape, inspiring The Flash to help the transition between franchises.
The Flash Movie Was Changed To Eliminate Future DCEU Setup
Originally, The Flash featured multiple DCEU cameos, including Henry Cavill's Superman and Gal Gadot's Wonder Woman. Although their role in the movie is unknown, their return was likely to set up a revamped version of the DCEU slightly altered by Barry Allen's multiversal adventure. When the end of the DCEU became official, the only thing The Flash needed to do to disconnect itself from a potential DCEU continuation was to cut these cameos. A complete reboot was never intended to be synonymous with The Flash.
The entirety of The Flash's multiversal plot likely remains the same, as Barry Allen's decision to travel back in time and its disastrous consequences are its focal point. Whatever the studio chooses to do in order to explain the birth of a new universe is mostly independent. Nevertheless, the confirmation of all the upcoming movies and shows in James Gunn and Peter Safran's DC Universe means that the events of The Flash can still be useful to explain the birth of a new universe in the future.
