Rumor has it Henry Cavill is done playing Superman, and while the news is not yet official, recent rumors that a Supergirl movie is in development bolster this morning's claim that Kara Zor-El will take point for a while in representing Krypton on the big screen.
With a popular leading man (likely) gone and the Man of Steel himself apparently sidelined for the indefinite future, it seems appropriate to ask that age-old question (posited sometimes by Lois Lane herself): Must there be a Superman?
The answer is yes.
One thing Zack Snyder's films got right, even if the critique that he told it rather than showing it has some merit, is that all of the positive impressions the world gets about superheroes flow from Superman. While Wonder Woman and Batman did good in the world, they did so while keeping their existence secret, or at least rooted in shadows. Superman stepped forward onto the world stage and served as something for people to strive toward.
You can see this expressed in the promotional material for Shazam!, where Freddie is clearly a Superman super-fan, and is likely the reason Cavill reportedly almost had a cameo in that lighter, more upbeat film.
Even in a Dark Knight Returns-inspired universe where Batman "came first," Superman gave superheroes their first public face. Nobody, after all, aspires to be Batman. Even his closest friends and surrogate children recoil when they start to sense that they are becoming too much like him (this was Tim Drake's entire arc for a while).
Solo superhero movies can easily exist in a world without a Superman, but if DC wants to carry on a shared universe, it would be difficult to do...and if they want to act like any recast characters still exist in a shared continuity with the other movies, it becomes even more fraught.
To continue the universe established in Batman v Superman: Dawn of Justice and Justice League -- even with significant changes -- it would be necessary to include Superman. His death and return was the emotional core of the team-up films, and from the first shot of Man of Steel all the way through to the final monologue by Lois Lane, Zack Snyder's movies were very much Superman's arc.
Given that Aquaman, Shazam!, and the two Wonder Woman movies are all origins of sorts, it would actually be simple enough to write the events of Man of Steel and Batman v Superman out of continuity quietly and begin building a universe with a different Batman and Superman, or one that lacks them entirely, but we already know from advance looks at Shazam! that is not what's happening.
The introduction of Supergirl would also beg the question: where did her cousin go? This could be written around, of course, by sending him into space, or through time, or something of the sort...but both the movies as they currently exist, and the character of Supergirl, are bound to Superman in a profound way that would be virtually impossible to undo without making changes that would alienate the audience even further.
If in fact Cavill is done, the question of how DC handles the most significant figure in the established world of its movies becomes an operative question, and the conversations that have been happening among fans and on film Twitter about how to retool the DC movies become less academic and more urgent than ever. Because the DC Universe needs a Superman.