will Sony (or Zeiss) make a fast 2.8 zoom that's for crop? like the Nikon 17-55i am looking to upgrade from my 18-70 kit and the only "good" option is the Zeiss 16-80 but it's 3.5-4.5i really love the Zeiss 24-70 2.8 but it's not wide enough and it's way too expensiveare there any plans for a crop version or is it because Sony is coming out with full frame that they don't bother with it?