When I see threads such as this I'm reminded just how miniscule the MFD market is and how challenging the economic crisis must be for MFD manufacturers and dealers.
Doug does make some interesting points and regardless of where medium format is at the moment there is a compelling case for the working photographer to own (or rent) more than one format or one system.
Whether there is a compelling case to own anything more than 30 megapixels is debatable and more personal preference than client dictates.
What Doug didn't mention is that no matter what the camera makers offer, current lithographic printing for standard page sizes means anything over 20 something megapixels usually requires downsizing for commercial printing. Even large format printing like outdoor, shelter cards, in-store is not designed or meant to be viewed at 3 inches but at a much further distance.
In the commercial and editorial world from a client's perspective, camera choice is usually way down on the list, if ever mentioned, so what we buy, what we use is more personal preference than an actual need to have x number of megapixels.
We can all guess at what the future might bring, but as I see my work purposed in a lot of different media and formats, the fastest growing segment is not tradition print, it's viewing on a computer or some other form of electronic deilivery and once you go to that medium megapixels are not that important.
In fact the changes I've seen in the last 5 to 7 years in photography have been more production related than anything that revolves around the detail of the capture. Pre production, shooting and post production routines have changed dramatically in the last half decade and most clients assume that with proper production, almost any professional camera the photographer choses will allow for the required results.
It's interesting that today there are volumes of reviews online about the Nikon D3x, basically applauding it as a medium format alternative, with the only real downside to the camera being the $8,000 costs.
In the world of medium format, even used, $8,000 is just the beginning.