The idea of a dedicated B/W digital camera which Alex is suggesting is really not so outrageous, I would suggest, especially so here in Europe where there is a long tradition of dedicated B/W photographers who work in this medium from preference. There is unfortunately a tendency among younger workers in an increasingly colour-dominated field to view B/W as just another sort of "effect" or filter which one can use to make certain shots look more interesting or old-fashioned, rather than having monochrome as the primary objective - indeed, the only objective, for some of us still.
It is certainly possible to have a commercially viable busines making niche products. In that sense, MF digital backs are certainly niche, with a very low global sales volume, but Phase One has made a successful business from them. Think also of tilt-and-shift lenses, large format view cameras, and rangefinder cameras, all of which have always had a relatively small market but which are still manufactured.
A dedicated B/W camera would be perfectly feasible for a company which already has a suitable body and lens system, because only the sensor and firmware would need to be changed. I would have thought it could be viable for Ricoh, or Olympus with their new Pen series, or even at the high end for Leica with a B/W M9. If there were to be real gains in acutance and possibly DR over the colour version, they could have a steady seller.
John