Is diffraction an increasing worry? Or, what's wrong with more megapixels?

Sanpaku wrote:

According to the Airy disk calculator at Cambridge in Colour, 4/3 and m4/3 sensors become diffraction limited at the following apertures:

12.5 Mpix: diffraction limited at f/8

25 Mpix: diffraction limited at f/5.6

50 Mpix: diffraction limited at f/4

100 Mpix: diffraction limited at f/2.8

• More Mpix would only improve large aperture lenses. Current kit zooms wouldn't benefit at all due to diffraction limits and lower quality (DxOmark rates the PZ14-42 as producing only 5 perceptual Mpix on 16 Mpix sensors now).
• The best m43 lenses were engineered to wring out the best from 12 Mpix sensors, and I suspect lens quality limits effective resolution to not much more, save for perhaps with the 75, 20, 60 & 45 macro.
• 16 Mpix means A3 (42.0 x 29.7 cm, 16.5'' x 11.7'') enlargements at 300 dpi. I don't really need photographic wallpaper.
• My RAW files already require 14.5 Mbytes each. They add up.

The advantage I would take advantage of from any resumption of the megapixel wars is in-camera electronic zoom. It would be nice taking a 32 Mpix EM-9 with just the forthcoming 150mm f/2.8 to go birding. Cropping to the center quarter would mean a fast, light, and compact 8 Mpix 600mm equivalent setup.