That said, Imaging Resource got 2,200 LPH of "strong detail" (MTF50?) out of the Sigma DP1 Merrill. They said complete extinction (MTF10?) did not occur even at 4,000 LPH. By comparison on their test, the 50D hit 1,800 / 2,600. (I put a question mark by the MTF values because I'm not sure if those are the values IR actually uses.) So for strong detail this would suggest the Foveon is 20% better, but for extinction resolution it would suggest over 50% better.
It should be noted that later versions of ACR yield higher extinction resolution numbers. Redoing the test with the 50D and the latest version of ACR may yield higher numbers, though there is clearly some advantage to Foveon in any case.
This is very interesting and why I asked my question in the first place. Even if this camera never comes to market it would be very
interesting to see what the advantages and disadvantages were.
Warning, somewhat off topic:
I know it will never happen, but it would be so cool to see digital bodies become more film like. I'm talking about interchangeable sensors. Obviously, sensors work in concert with other integrated circuits so it would have to be an interchangeable sensor/processor board with a common bus to work with various bodies. But how neat would it be if you could have a light compact body (including mirror assembly, af, light metering, lcd, etc) as well as something 1DX style for high fps, weather sealing, etc. AND then have different sensor cards that worked with either body to choose from based on what you were shooting... a large megapixel sensor for landscapes and studio work or something with big photosites for low-light work. New sensors could bring new imaging features while new bodies would bring new AF, metering, wifi, gps, etc features.
Suppose this were how it worked today. Imagine this scenario: You have the choice of a 5D Mk II, 5D Mk III, 6D, 1DsMk III, or 1D X body independent of your choice among those sensors. Imagine you have bought into the Canon system in 2008 with 5D Mk II body and its 21.1mp sensor. Now the 5D Mk III line launches as body only, sensor only, or as a kit. You could choose to only upgrade the body and use the existing sensor to gain improved AF, construction, light metering with the trade off being you would still be limited to 3.9fps (I realize this sensor did 6fps in the 1Ds Mk3, but even in my imagined scenario Canon software locks some features out of non 1D bodies). I think a lot of people who upgraded from 5D Mk II to III would choose this path to save some money. Now imagine this hypothetical 75megaphotosite sensor comes out and it's S___ past ISO 400. If that's the actual case, Canon may well decide it's not ready to go on the market, that it couldn't really survive as a whole product. However, it might succeed just as a sensor card upgrade.
I DO realize there are a ton of challenges with what I am suggesting but this is not pie in the sky stuff. Honestly, the biggest challenge might be how it would shake up the pricing/shopping paradigm we currently have. Difficulty forecasting how many of each component they would sell and calculating a break even price on their development costs, etc... that sort of thing.