Justice League 3 would have ended with Superman and Lois' son becoming the new Batman, according to director Zack Snyder. Zack Snyder's Justice League has finally landed on HBO Max with four years of fan anticipation behind it, but the film was never meant to be a standalone and was supposed to be the first in a Justice League trilogy. Snyder has spent the past few weeks leading up to the release of the Snyder Cut revealing what would have happened in his planned sequels.
Justice League 2 would have featured the team facing off against the Legion of Doom, ending on a note where Darkseid kills Lois Lane and Superman succumbs to the Anti-Life equation, setting up the Knightmare future teased in Batman V Superman: Dawn of Justice and Zack Snyder's Justice League. The third film would have seen an invasion by the New Gods and taken place in the Knightmare future. Snyder has even revealed that the third film would end with Batman dying, but now fans know there would have been another Batman.
In an interview with Vanity Fair, Zack Snyder revealed the plan was for the son of Clark Kent and Lois Lane to take on the mantle of the Batman. The child's name would be Bruce Kent and he would not have any of his father's powers. The scene would take place in a flash-forward, years on in the future when Clark and Lois take their son to a familiar location and ask him to take on the mantle of the Dark Knight. Snyder said:
"It was going to be Lois and Superman’s son...Twenty years later, on the anniversary of [Batman’s] death, they take young Bruce Kent down to the Batcave and they say, ‘Your Uncle Bruce would’ve been proud if you did this.'"
This appears to take the place of Snyder's original intention, which would have seen the child be Bruce Wayne's kid instead of Clark Kent's. The original plan would have seen Bruce Wayne and Lois Lane begin a romantic relationship after the death of Superman, and would further complicate Bruce's feelings about bringing Superman back from the dead. Warner Bros. was not keen on this development and it was dropped, despite the idea of Batman having a son being a popular development in the comics.
The ending that Snyder envisioned strikes a similar note to the end of The Dark Knight Rises, which finds Joseph Gordon Levitt's character Robin John Blake discovering the Batcave after Bruce Wayne has left Gotham City, with the ending implying Blake will become the new protector of Gotham City and that Batman is a symbol that will outlive any one man. This concept actually blends two recent popular stories in the pages of DC Comics into one idea. Other people taking on the mantle of the Caped Crusader besides Bruce Wayne has been explored in media like Batman Beyond and the recent comic Future State while Superman being a father has been seen in Superman Returns, the pages of DC Rebirth, and now is the main plot of the recent CW hit Superman & Lois. Superman's son becoming the new Batman in Justice League 3 feels like the ultimate end to the arc that began with the two as enemies in Batman v Superman.
Source: Vanity Fair