Apple's display line is in dire need of a refresh.
30" is the top end. There's nothing packing more pixels that's also commercially viable. The 1920x1200 is the largest "practical" display, where 1920x1080 is rapidly becoming the new standard, even available at Walmart. Only a few things have happened in displays lately: Glass/glossy coatings for better saturation and LED backlighting. Every Apple display except the 30" is glossy, though you can order a MacBook Pro with a matte screen, and every display is LED except the 30". There were some 30" LED displays about a year ago, and they were $4000.
There are just too many competitors in the display market to really put that much effort into it. With the exception of the LED 24, which is much more about convenience than cost effectiveness, there's no real benefit to picking up an Apple display.