It seems to me that if you don't mind having a battery that gives only 150 to 200 shots, or having a battery three to four times larger, then CCD's would be fine for 35ff cameras. But I doubt that most people would like that.
Another factor is where the R&D dollars are going. CCD sensors cost more than CMOS sensors, because CMOS sensors are made on the same lines as any other chip. But CCD's are made so differently, that they need special lines. Because of that, the cost to manufacture is much higher, without many other benefits for most people. As for CCDs being used for most compact cameras, that's still true, but won't be for the future. These chips are so small, and so many cameras use them, that the cost is reasonable. The cheaper electronics in those cameras outweighs the slightly higher cost of manufacture for those small chips.
Because every db of noise reduction is needed for those small chips, CCD is still the way to go. we notice just how bad the higher ISO performance those cameras have, due to the small sensor, the cheap electronics, and the CCD.
As far as MF goes, the story is opposite to that. Price is almost of no object, and the best electronics is used, often with some form of built-in refrigeration to keep those large chips cool. CCD's get much noisier when they heat than do CMOS.
Eventually though, everything will move to CMOS, as their performance is rising faster than is that of CCD.
It's like film. Years ago, when digital began to get useful in the way of quality, about the time the Canon D30 came out, my Kodak partners (we processed professional kodachrome film, the only lab to do so) and I discussed the future of film and digital.
Their opinion was that film had come about to the end of its possible development. There was room for improvement, but no major performance enhancements were possible without much more effort that was affordable. Digital was seen as advancing so rapidly, that there was no way the money could be spent on major film development efforts.
The same thing is coming true for CCD vs CMOS. I've read number of papers on this over the past few years. CCD has come a long way, and it's felt that it doesn't have that much more to go. A few years from now, and its advances will peter out. but CMOS is still in its infancy, and has a way to go.
There are actually some newer technologies in the lab that will give better results than either, but they are a ways off. They'll likely appear just when needed, as this is usually what happens.
