Zack Snyder's Justice League will be significantly different from its 2017 theatrical counterpart, but it won't retcon any other film from the DCEU.
Zack Snyder's cut of Justice League won't retcon any other DCEU film aside from the 2017 theatrical version of the film. After more than two years of clamoring from the Release the Snyder Cut movement supporters, Snyder's original vision for the Warner Bros. and DC Films' ensemble movie is officially seeing the light of day. During a watch party for Man of Steel, Snyder himself confirmed that his Justice League will be released on HBO Max in 2021.
It's currently unknown what form Snyder's Justice League will take when it rolls out, but reports suggest that it can either be a 4-hour movie or a TV mini-series, with the filmmaker personally pitching the project with episodes and cliffhangers. Snyder has apparently also reached out to his cast for potentially returning for additional work and some reshoots. Given all this, coupled with how the theatrical cut of the film significantly deviated from the director's original plan, it's curious how the new version of Justice League can impact the DCEU as a whole.
Fortunately, regardless of how different Snyder's upcoming Justice League will be, it will only retcon the 2017 film, meaning it won't cause any major continuity issue for other films in the franchise. After the Joss Whedon-assembled cut of Justice League disappointed at the box office, not to mention the controversy surrounding it, Warner Bros. took more than a year hiatus for the DCEU to reassess their plans for the struggling superhero film series moving forward. The franchise made its triumphant return via James Wan's Aquaman, which was primarily separated from everything else that happened in the bigger universe since much of its story took place under the sea. The DCEU continued with smaller-scale films such as David F. Sandberg's Shazam! and Cathy Yan's Birds of Prey. Both projects alluded to heroes like Superman and Batman, establishing their existence in the same reality, but other than that, their stories were character-driven, with no other ties to what happened to Justice League.
Similarly, Zack Snyder's cut of Justice League won't also pose any continuity issues with Wonder Woman 1984, whose story is already locked. While the Patty Jenkins and Gal Gadot film is slated to release in August 2020 - before the upcoming HBO Max project does some time in 2021 - its story is set in the past, so any changes that Snyder makes from the theatrical version of the 2017 ensemble film won't have any impact on the sequel. Meanwhile, regardless if its a total reboot or a sequel to David Ayer's 2016 blockbuster, fans can also expect Snyder's Justice League to have minimal to no effect on James Gunn's The Suicide Squad, which appears to be largely set in its own pocket of the DCEU like its predecessor.
With all things considered, the release of Snyder's Justice League will only really change the theatrical version of the movie. There's no major character development for the six heroes on the big screen bar Arthur Curry (Jason Momoa) assuming his rightful place in Atlantis, which doesn't have much bearing to the events of the ensemble film. In hindsight, Warner Bros. actively moving away from the events of Justice League now allows Snyder the creative freedom to do whatever he wants to do with his upcoming version. There's no narrative thread from the ensemble film that has continued in the DCEU, therefore, he's not beholden to any continuity established after his exit from the franchise.
