It's funny I was searching for that data just the other day.
There used to be two core reasons for f1.2 lenses, light gathering, at which they always made huge image quality compromises, and very narrow depth of field. With modern iso capabilities the light gathering aspect has become less important, but the ultra narrow dof is as important as ever. Canon have always delighted in their lens selection and the speciality lenses have always been a key component of their lens system. I don't see the f 1.2's going anywhere, interesting that they have come out with a $5,000 CN-E 35 T1.5 before an EF 35mm f1.4 MkII.