Back in January 2023, James Gunn, the co-head of DC Studios and the writer/director behind Superman, announced a hefty first slate of movies and shows for the franchise, all packaged together as a Phase 1 of the new DC universe,

“Not yet” implies that the movies coming now, and later, could be building to that—and when asked if the Justice League plays a role in what Gunn has planned for the overall DC Universe story, he simply replied, “Sure.”

In spite of 'Superman' featuring many DC superheroes, the Justice League doesn't exist in the DCU, but that could change in the future.