There are still a reasonable number of light aircraft manufacturers that make bi-planes. E.g. Aviat Aircraft still make the Pitts Special aerobatics bi-plane.
While I know that there have been quite a few different variants, are there any other planes that have been in production longer than the Pitts Special (61 years)? I know the Piper Cub might count if the Super Cub is considered a variant, rather than a new design?