Within the next few months I'm pretty sure we'll get the second "modular" camera to be announced (the Ricoh GXR being the first), and no, it's not coming from Nikon. But given the design of this upcoming camera, I have to wonder if the camera makers are thinking clearly. The reason people buy new serious cameras is mostly because of the sensor and digital logic. That's the part that needs to be modularized. (In the film days it was lenses, and the companies correctly figured out how to modularize that.) Moreover, camera companies are missing out on added sales: who amongst us serious photographers wouldn't buy one or more other sensor modules (FX, DX, HiRez, LoNoise, B&W, IR, etc.), and who wouldn't keep updating the sensor module with each generation if we didn't have to buy a whole new body with it?
Here's a tip to the camera makers: package the whole sensor modularity thing as a Greener way to keep your camera current and mock your competitors for making you throw away perfectly good camera bodies in order to get the benefits of a new one.