Thanks for bringing up another thread like this, and no I'm not being sarcastic.
I am so with you on a 21.5"/27" display. I personally would swoop up two 21.5" displays without question.
I'm also tired of seeing the naysayers shoot down these threads down too. This should not be a one-size-fits-all issue. If anything, new displays in those sizes would compliment the existing imac lineup and 21.5" displays would sell with it's lowest price point, regardless of its smaller size. Remember, it can also support 1920x1200.
And finally, on that note, not everyone who uses an imac or a Mac Pro are graphic artists (me included), so i hate to see other professionals get robbed of the chance for a smaller, more inexpensive display. I simply don't have the need of an overly large sized display, but I would still love to be able to afford an Apple-grade display. That said, I would be absolutely content with a 21.5" LED display.
Please bring it Apple!