[shuttertalk]

In an ideal world, I'd love to see cameras such as Canon's 1-series offer interchangable sensor cartridges. It would enable Canon to go back to having a single 1-series body and then offer a choice of specialty sensors that the customer can buy and interchange as they might a focusing screen. To me, this makes as much sense as having interchangable lenses or the ability to use different film in film cameras.
Imagine a choice between 21mp (current 1DsIII/5D2 sensor), 10mp high-speed (current 1DIII sensor - low-res but 10fps), 10mp foveon (low-res but 48-bit HDR), 16mp b/w (no bayer filter so monochrome only, medium-high-res and medium-high DR).

Interesting concept... you should probably rush out and patent this - I could see this happening in a couple of years' time. FWIW I think the manufacturers would probably lean towards sensor "options" rather than user-interchangeable ones but that's just me...