Banno also addressed the idea of a sequel to the film in which Godzilla would have fought a 2nd Hedorah that appears in Africa. Banno later revealed that that story was just a fling and that he had intended to make a Hedorah spin-off rather than include Godzilla in it.
A sequel idea before that was originally planned to have Godzilla battle against a Mutant Starfish.
An IMAX 3D remake of Godzilla vs. Hedorah was in its planning stages around 2004, around the time in which Godzilla Final Wars. The project however was too short (around 60 minutes total) and was rejected by Hollywood. However after Banno pitched uping the runtime to 2 hours, after Legendary Pictures was put on the project, the idea eventually morphed into Godzilla (2014)!