I am far from technical on this topic, but they maybe waiting for sCMOS (Scientific CMOS) development to commericalise. There is one example of a commerical sCMOS chip already available:
http://www.scmos.com/
A summary of sCMOS development and goals:
http://www.photonicsonline.com/doc/s...-overview-0001
The ASI 1600 has low noise and sensitivity improvements, and the high USB3 and frame speeds, but sCMOS should be a bigger leap I would imagine. I don't know where the cross over point lies.
Bert, I think there are some 2x2bin examples in the Cloudy Nights Beta Test thread.