There are a number of patents from many camera companies for interchangeable sensors, but so far, the idea has been impractical simply because new technology requires additional connections and electronic speeds that were not foreseen two or three years earlier, and getting tied to out of date technology isn't something engineers want to do.
Right now, many sensors are switching to 8 channel readouts, what will be have in 3 years? 12, 14, or 16 channel, and what speeds? The motherboard and processor tie you down to todays technology pretty well. It also ties down any improvements in autofocus, video, or nr among other things.
Its not really such a good idea when you think about how much it shackles you to obsolete technology..
Its hard to believe that we will see practical interchangeable sensors unless its just for easy replacement of a damaged part.
That is true with the presumption that the user is going to put a "newer" sensor in a "older" body. But no one tries to use a quad core processor with a motherboard that is for Pentium 4. When quad (or hexa) cores came we had to change our mother boards. But there are different versions of the quad cores that can be fitted on the same mother board that can fit all of them. Computer technology did not get stalled for that. Like that we shall be having multiple sensors for the same body. When the next body comes if that does not fit the sensor I have I will have to upgrade (as I do with computers) - sell this body and sensors as instead of just selling the body and buy the new sets.
That is I am thinking of a situation where there are several concurrent sensors for the same body? Like say interchanging an "without AA filter" sensor with an "with AA filter" sensor (something like D800 and D800E in the same body). Like the different digital backs for the same camera - I think some medium format cameras do that, do not they?
Of course my opinion is based on my very rudimentary understanding of electronics.