The problem that I have with Canon is that they are doing this intentionally - release incremental upgrades to their bodies. Take a look at their bodies starting from the xxD and upward. Small upgrades that are not worth upgrading for the IQ. The 60D is a step backwards from the 40D in IQ, as an example. The 7D is a pretty nice camera, but does poor in low light conditions.
You know, back in the film days, the camera contributed virtually nothing directly to image quality. If you wanted different dynamic range or color rendition or whatever, you didn't blame the camera; you popped in a different type of film.
What differentiated cameras then is exactly
what differentiates the 5DIII from the 5DII -- and, not coincidentally, what makes the 5DIII a significantly better camera than the D800 as well.
Specifically, it's all those non-sensor things, like autofocus performance and frames per second and metering and ergonomics and the rest. Even more importantly is the whole system -- the lenses you can mount on the camera.
With the exception of the very last top-of-the-line pro body film camera Canon ever made, the EOS 1-V, the 5DIII blows away every single film camera Canon ever made on any spec you care to mention -- and the only spec that the 1-V bests the 5DIII on is framerate (10 FPS v 6 FPS). Not only that, the 5DIII handily bests all other pro digital bodies Canon has ever made in pretty much every spec, except for the framerate of the crop sensor models.
And, oh-by-the-way, it's got image quality that simply doesn't exist in the film world (I dare you to make a 36" x 54" 135-format film print that comes anywhere close to what the 5DIII can do), image quality that's on a par with or superior to every other camera in its format on the market save for one single model from the competitors.
And, also-oh-by-the-way, it's a high-definition large format high-speed motion picture camera.
And, did-I-mention, Canon glass stomps all over the competition, what with the TS-Es and the supertelephotos and the MP-E and on and on and on.
And yet that's somehow still not enough? Canon is holding back?
Say, any of all y'all complainers get your invisible pink flying unicorn ponies from B&H? I hear they were supposed to start shipping after Pesach....