For someone who was once “a hero nobody knows,” Saitama is certainly developing some notoriety. For example, he might end up becoming more famous worldwide, if Sony has its way. A live-action One Punch Man movie is in the works. [Thanks, Variety!]
So far, it doesn’t seem like this project is too far along yet. Sony does have the two producers announced. Arad Productions, headed up by Avi and Ari Arad, is in charge of it. Recently Arad Productions was involved with the 2017 Ghost in the Shell movie, Spider-Man: Into the Spider-Verse, and is connected to the upcoming Metal Gear Solid film.
As for the One Punch Man movie script, the people working on it are Jeff Pinkner and Scott Rosenburg. The two are writing partners who have worked on multiple films together. Most recently was Jumanji: The Next Level, though the two also worked on Jumanji: Welcome to the Jungle, Venom, and Salamander. Rosenberg also recently wrote the Hulu High Fidelity show, while Pinkner is working on Creature from the Black Lagoon and The Amazing Spider-Man 2.
Most recently, One Punch Man received a game adaptation. People can find One Punch Man: A Hero Nobody Knows on the PlayStation 4, Xbox One, and PC. It is a fighting game where, in the campaign, people create their own superhero and fight alongside characters from the series and Saitama.
The One Punch Man movie is in development.