yes, you are dreaming! ;-) just kidding!  

somebody might be able to mount the sensor at the focal plane point on a
MF SLR, say, with a flex cable or by hacking the camera body (lens removed
etc.) so the sensor now sees what the MF lens is projecting at the focal
plane.

The big pain here is that most MF SLRs with interchangeable backs
put this point dang close to the camera body (few mm.) so matching up is
problem prone and doesn't allow much slack for sensor cabling & mounting.

One solution is to do as with a polaroid back, using a fused and polished
plate of parallel fiber optic fibers to conduct the original image to the
sensor some distance away from the camera focal plane. Problem here is the
fused fiber plate is big $$ by itself ;-(

my preferred solution is to use a lens to re-image the aerial image from
the focal plane onto an existing digicam lens, allowing you to use the
existing MF slr.. lenses at full format, but at whatever the resolution of
the digicam might be, and reading out on the digicam LCD screen.

Sort of like taking a photo with your camera thru an afocal telescope at
the Grand Canyon, but here something like a closeup lens is allowing the
digicam to see the aerial image at the focal plane (say 6x6cm SLR). If you
can remove the lens from the digicam, this might be even easier to setup
and do, esp. if you have a full range of camera controls and some way to
interlink to the MF SLR to trigger the digicam.

finally, if there is a big enough market, something like silicon film's
idea (a drop in cartridge shaped digital sensor and electronics?) might
work, esp. for those cameras with removable backs or inserts? But at
25,000 MF sales per year in USA (per NYIP estimate), that isn't much of a
market, esp. when you consider all the models out there, and low volumes
kill you on cost with leading edge sensors and custom electronics and
software ;-(  

this is why I would like to see someone like Sigma/Foveon (16 MP device)
come up with a digital camera that use _just_ the lenses of popular
cameras (preferably using a simple adapter for auto diaphragm operation
etc.), including not just 35mm RF/SLR but also adapters for MF and LF
mounts too. Such a design would be like third party lenses in reverse,
anybody with any lens could buy this DSLR, and use it with the right
adapter and preserve their investments in their lenses, yes? For MF folks,
the adapter might include a deluxe adapter option, with some shift/tilt
function, to take advantage of the larger coverage of MF optics?

The 22 MP sensors (Sinar..) are 45x60mm with an active area of about 39mm
x 50mm. That kind of chip might be close enough for many 645/6x6 users
(some are paying big $$ today for it ;-) in MF depending on the price?
And again, 22 MP may be "good enough" for many MF users and needs too ;-)

grins bobm