Diffraction is a physical limitation to resolution, and even though I usually agree with you, TTJ, I think the tech is getting close to where it makes a difference in some practical situations. Without having looked at the A77 images and just based on the increase in lateral resolution, I would think that f/5.6 is probably not where the physical limitation is on DX for 24 MP (my guess is closer to f/8, but someone could crunch the numbers).
Though f/8 is a sweet place to be for a lot of photographers, it's not that the technology isn't useful to anyone; there will still be people who want those 24 MP and are going to shoot at f/4 or f/2 or some other large aperture most of the time. For them, diffraction is a non-issue and they can print their wicked huge prints (or just gush about how much data there is in their pictures—look at those nose hairs! I've never seen anything like this before). I think more photographers are in this group (less the nose hairs) than the group for which diffraction is starting to matter, which is why manufacturers just keep increasing resolution like low res is going out of syle.
It's the landscape photographers that are probably going to realize that 24 MP (or 32, or whatever) is not going to help them on DX because they're already running into diffraction at the apertures they set. They can always go to larger format, though.
Niko, shouldn't we start a 'DX is dead' thread, just for old times' sake?