The first surprise from Dragon Ball Super: superhero, the saga's feature film slated for 2022, was shot in 3DCG, which few expected from a brand of this size. A trailer followed with lots of interesting points, but one that caught the attention of fans in particular.
Even if Broly appeared for very few frames in the trailer of Dragon Ball Super: Super Hero, the Super Saiyan was canonically introduced by the final film in the franchise. Given the theme of the film and the fact that it did not appear in the Dragon Ball Super manga, the Saiyan's return was not expected. And at this point What role will Broly play in Dragon Ball Super: Super Hero??
The greatest likelihood is focused on a supporting role, with a Broly simply acts as Goku's sparring partner and that will therefore appear in some scenes. Even with a little glimpse, Broly cannot make a consistent appearance in this film, which seems to want to focus on other characters.
Also, there's a chance the Broly we're seeing isn't the real Broly. In fact, during one of the stages of the trailer we see Goku, Vegeta and Majin Buu in evil version on some large screens, something that still needs to be explored, but if the new enemies have a method to recreate an evil version of the protagonists, the same could have happened to the legendary Super Saiyan. That would make him an antagonist of the film, even if this time only for a short time.
The last option is that Broly is the film's famous superhero and that will help the protagonists in the fight against the mysterious opponents. The main hypothesis, however, remains the first or with a Broly with a more withdrawn role in the film. We'll have to wait for the next information on Dragon Ball Super: Super Hero to get a clearer idea.