Hi Carl,
what a wonderfull world for us that would be!
BUT:
the camera manufacturers donīt produce CCDs or CMOSs. most of them by them of either kodak or sony. the result of your idea would be the end of all camera makers as there would be over a few years probably enough bodies on the market that can hold a new sensor. so they are not gonna do it.
Also, it is not just done with the sensor and a software upgrade. the sensor talks to some surrounding electronics first and they are a team that wouldnīt work with a new sensor (even pretty standardised PCīs with ZIF sockets for the CPU donīt accept a new processor just like that). so you would have to change the whole motherboard (or what is called in camera).
and since a new board would in many cases and for various reasons need a different mounting or just more space, you would have to also exchange the housing. different housing and different sensor probably means different cooling stage connection as well and so on...
BUT:
I would love to get myself the new Canon 120 Mpixel sensor and mount it in my 450 for a couple of houndred bugs
the idea at least has some sustainability aspects
Cheers!