Cast iron tubs are possibly still considered the "cadillac" of tubs, but I don't think they are in the majority of installs anymore. First off, a "high end" remodel today often calls for some kind of soaking tub, whirlpool, or some version of a 'garden tub'. Most of those are acrylic. And the porcelain on resin, such as americast, also take a portion of the market away from cast iron.
I would be intersted to see industry figures on what percentage of each kind of tub is used in remodels, and new construction.