Of course eventually all image sensors will go the way of Moore's law in computers, they will get close to 100% QE and then thats it. They will never get any better.
Sadly canon doesnt make them, but Id love to see how one of their DSLR sensors would go if its bayer filter array was removed, making it a pure monochrome sensor.
I believe Astronomik will soon release a "multi emission line" filter, essentially a narrowband filter with all three emission lines, thus allowing a DSLR or CCD single shot colour camera to do true colour narrowband imaging where the red, green and blue pixels will get light.
A clever idia that never really took off was the "
foveon" sensor where each pixel recorded all colours. Photons would penetrate to a certain depth according to colour and the sensor differentiated that. So far however the sensor doesnt seem any better, and isnt that widely used.
DSLRs have one advantage, economies of scale. Thousands of DSLR CMOS sensors come off the production line for each Kodak CCD sensor. DSLR companies can thus spend a heap more on R&D than Kodak can on its CCDs
Personally, if I was SBIG Id approach Canon as to making a run of monochrome 11 MP CMOS sensors, with 16 bit ADC, single stage peltier cooling, then proudly sell them for < $3000USD and still make a profit
