How much would Canon make by updating the 50CM with modern trimmings and doubling the price? I would pay ~700 for a USM, IS, weathersealed, circular apertured 50/2.5 macro.
I rather they upgrade the 50mm f/1.4 to carry the nice USM ring type AF, weathersealed or not, don't really care. If you want weathersealed, get the L. IS for a 50mm fast prime, don't really need it. And I much prefer longer focal length macro, 50mm macro is not really my taste.