No, he's not referring to something like Dracula: Dead and Loving It, which is the last film he penned for the big screen. He says that he's developing a serious horror film with writing collaborators Rudy De Luca and Steve Haberman called Pizzaman. Currently, there's no word on the plot, but considering the title, I think it's safe to say that it will include a Pizza man. Perhaps a killer pizza man?
What's surprising about this news is that Brooks seems to have a direct hand in writing it, although his previous involvement with horror/eerie/dramatic* films, like The Fly and The Elephant Man, were only on a company/producer level. Now if only he could bring us one more, really good comedy, I'd be overjoyed. But then again, some of his best stars are gone now, so maybe it's good that he just moves forward.
What would you rather have from Mel Brooks: a comedy or a horror?
*Edited for clarity.