Rengoku isn't part of Funko's recent announcements of incoming Demon Slayer Funko Pops. However, since he's one of the most popular characters in the series, likely, he will eventually have a Funko Pop version soon. Luckily, you can still enjoy Rengoku in other forms in the meantime. There are already Nendoroids of him available, as well as many scale figures and statues.