I wonder if, optically, this is based on the existing 70-300mm model, which is decently sharp but suffers from horrendous PF, CA & overall tone.
New optical system optimized for digital cameras achieves top resolution in the 70-300mm class with specialized glass elements including an XLD (Extra Low Dispersion) lens
This lens advanced optical design employs a sophisticated XLD (Extra Low Dispersion) lens element made from specialized high-grade glass that has lower dispersive properties than standard LD lenses (where refraction causes the dispersion of white light into spectral hues). The dispersive properties of the XLD lens are at a level similar to fluorite, and in combination with a LD element make for an optimal optical design that delivers best in class resolution with advanced axial chromatic and magnification aberration correction - major inhibitors of image quality enhancement. The result is a lens that delivers sharp contrast and better descriptive performance throughout the entire zoom range.
Is it too late to add USD to their 17-50mm VC? (completely wishful thinking/joking)