I have the exact same fear. I think that the new iPad will ruin us in terms of expectations for screen quality.
This is the wrong way to look at it. What you need to realize is that if this trend of high pixel density displays takes off as much as it is with the iPhone 4, 4S and now iPad 3rd gen, then it's going to "force" the display manufacturers to adjust to market expectations.
Here's a possible future scenario I can imagine. It's a two part process where display manufacturers and graphics card manufacturers work together on a new standard. When in a 2D environment, like your Windows or OS X desktop, your GPU would be sending a high pixel density signal to the monitor. Current monitors are 96ppi roughly. Lets multiply that by roughly 4 for that "retina" level to 374ppi. This would ease eye strain when reading text, working on documents, browsing the web, and generally make the interface smoother. The down side to this is your resolution on a 24" monitor would be around 7680 x 4800. A resolution even the best GPU's currently cannot handle in 3D gaming applications. So have a 2nd mode strictly for 3D gaming / applications built into the displays and a 2nd signal type from the GPU's that makes clusters of 4 pixels display the same color, effectively lowering the ppi back to roughly 96. This would lower your resolution to 1920 x 1200 which most graphics cards these days are able to handle without much trouble.
Until such a time that GPU's are able to render "retina" resolutions in fullscreen 3D this would be an adequate solution. It could even go so far to be dynamically activated in the case of playing a windowed game so only the part of the screen displaying the game receives the pixel cloning, leaving the rest of the screen looking just as sharp.
Man! What an epiphany! LOL!