Manufacturers are going back and filling out their high-end lens lines, having satisfied demand for well-priced, digital only f/4-5.6 zooms.
A new round of full-frame, pro-oriented zooms are coming out for the expanding ranks of full-frame bodies. These new lenses pack the advances in lens designs and coatings that were developed for digital-only zooms.
Pros upgrading to cameras with higher resolution imaging sensors are upgrading their lenses, too. Why? Because their older legacy optics aren't always sharp enough to show the finer detail a 16 or 21MB sensor can capture.
Demand is growing among midlevel DSLR owners who are discovering what f/2.8 can do.