I don't think we currently have enough pages about podfic for a separate category. Pages like Written by the Victors (podfic) have Category:Audio, and many (if not most) pages about fanfic that mention a podfic don't have any additional categories. Interestingly, we have a separate category Merlin Podfic filled with pages about fanfic, so the question is do we want all fanfic pages that mention a podfic to have an additional podfic category? Personally I don't think it's necessary.