But that's not quite how it works, you see, if HiDPI was enabled, the resolution would stay the same, only the pixels per inch would quadruple, so what was once a screen with a resolution of 1280x800 containing 1024000 pixels, is now a screen with a resolution of 1280x800 containing 4096000 pixels. So its the same resolution, only much sharper.
Applications not designed with HiDPI in mind would presumably look a little fuzzy compared to the higher resolution graphics, but would be scaled to size, similar to how older application icons look on the iPhone 4.
So what you are saying is, that one black pixel on some web banner or Photoshop tool icon would actually be 4 black pixels.... And what is the distinction for wanting to view in it's actual pixel size vs interpreted.
I mean, I'm a designer and I wouldn't want that, I need the extra screen real-estate, but I also want everything to be scaled so it is a 1:1 pixel interpretation of visual assets