Kenny,
A google search turns up CMOS sensors being sold with 80 micron pixels (just not in DSLRs), so hundred microns should not be a limit. I have used silicon photodiods in the 250, 500 and 1,000 micron sizes, and cmos diodes should be possible too.
It wasn't that long ago that we didn't even have 6 megapixels. I have a full page image printed in Natures Best: a 3 megapixel image, and I've sold 16x18 inch prints in galleries.
http://www.clarkvision.com/galleries...ght.f-600.html
But all this does not address that fact that the DX0Mark benchmark does not appear to include sensor resolution, especially for focal length limited situations laikt that often encountered in bird photography. But I do agree that 12-18 megapixels in APS-C sensors is the optimum in getting high enough signal-to-noise ratios and enough megapixels.
Roger