Well, if you're willing to drop $30K for a P45 (39 megapixel) digital back and another $10-20K for an MF camera system, you too can (maybe) have 4x5 resolution in an MF digital platform:
This is still a Bayer-array design, pixel pitch is 6.8 microns (Canon 1Ds2 is 7.2 microns, Nikon D2X is 5.5 microns). Shipments reportedly start in November.
Of course, you'd need to first confirm that your MF lenses have at least as much resolution as the sensor. Plus you'd still need to additionally invest in a geared digital view camera platform (with a separate set of lenses) if you want camera movements. Plus it would be nice to invest in an MF camera manufacturer that will still be around in a couple years (Contax and Bronica are already gone; Mamiya is betting the farm on its ZD; Rollei and Pentax are running on fumes; and Hasselblad is reportedly becoming uncooperative with third-party digital back suppliers). Plus 35mm digital lenses are approaching resolution limits, who knows if Canon and Nikon will forever abstain from invading a higher-end market?
I presume a 39 megapixel product will further reduce what little 4x5 film utilization remains in high sales volume commercial applications. And of course the eventual DNG raw format support is a good thing for all digital photographers. But obviously they've got a long ways to go to address the fine art and upscale amateur market pricepoints.
Guess I get to keep my 4x5 a little bit longer...... :-)