But that is beacuse the current options are not affordable for 'most' photographers.
Given the chance to use full frame, I doubt many would opt to use cropped sensors unless they provided ergonomic benefits such as m4/3's.
As a flagship model, Sigma could have done well to read the market and where it is heading. Full frame is becoming the standard in the professional photography market.
Cropped sensors were once simply only because of a lack of technology. 10 years down the line, full frame dslr's will be the only types sold. Again it just feels like developers are only getting to the half-way mark with all the new products.