It is possible to just use smaller pixels, so you can cram more pixels into a small sensor. That’s what’s been happening with consumer digital cameras. The problem is, if you reduce pixel size, each pixel gets less light (given same optics, etc). But the readout noise is largely unrelated to pixel size. So you need a longer exposure time to achieve the same signal-to-noise ratio. In other words, reducing pixel size reduces sensitivity. (Same thing happens with film - if you use finer grains for improved resolution, you end up with a lower ISO rating.)
The only way to get around this is to increase the physical size of the sensor. Unfortunately this isn’t easy to do for digital, because large pieces of semiconductor are very expensive. And the price won’t come down fast - the usual way of making computer chips cheaper is to make them smaller, but obviously that won’t work here. So I expect medium-format and larger digital camears will remain prohibitively expensive for many years to come.
Basically, right now, there’s enough resolution in the digital world to equal MOST film. I would think that a low ISO 8x10" sheet of film on a view camera with a quality lens would still outdo any currently available digital back for MF.
However, generally:
Today’s compact digital cameras (5-10MP) will resolve about the same as 35mm ISO 400 or 800 print film. (The problem is the small sensor which equals greater noise. This is why a 6MP image from a DSLR will produce a higher quality print than a 10MP compact, lenses aside).
Today’s average DSLR (6-8MP) will outresolve a 10MP compact (except for the new Sony with APS sensor), and will essentially equal 35mm ISO 100 print or slide film for resolution.
Today’s top DSLR (1DsII - 16.7MP) will equal the average resolution of medium format (645) film, and outresolves all 35mm films.
Today’s top Medium Format digital backs (like Phase One’s new 40MP back), will rival 4x5" and exceed the film they replace (645 format).
They’re in the discussion. My first link was to Sinarbron! But we kind of hijacked into image quality concerns, since image quality is why many people use larger formats in the first place.
I guess a simple answer to the OP is order here, so:
YES. In fact, they already have.