Kodak Unveils 50MP CCD Image Sensor
Old digital backs are still for sale on the market because they have no moving parts to fail. They work great.
Some of them have to be tethered to a computer.
Pretty soon there will be a good surplus of used 22MP backs on the market for about the price of a 1DS MKIII ($8000). I think the mamiya ZD is trading at $10k, brand new, with lens and camera body included.