There is a move afoot, via Lloyd Chambers' website, diglloyd (actually his blog), to get Phase One to produce a monochrome version of one of their digital backs. This then knocks onto Kodak, who produce the sensor. To read the whole thing go to the post of 26th July and read forward from there.
As Lloyd points out (and demonstrates with examples) you need far fewer pixels for the same resolution in B&W compared to colour - interpolation of data is a killer for detail. This means that cheaper sensors can be used assuming that more pixels = higher cost. I base that assumption on the fact that some makers are selling low res (4-5MP) cameras now for around $100. No frills, basic cameras. Put a monochrome sensor in them and I'd snap one up in no time.
If this is successful, maybe there will be a move to introduce monochrome sensors into other camera segments, maybe in line with my earlier thoughts on the subject. How about an exchangeable sensor DSLR? Canon used to make an exchangeable back film SLR, so you could run B&W and colour film side-by-side. Then would open up the whole notion of an upgradeable camera: slap all the important chips & stuff on a unit that slots in & out of the main body. Modular cameras for the masses.
It'll never happen, of course, but one can dream.