During a BUILD 2011 presentation, Microsoft told Windows 8 developers to plan their artwork for High DPI (dot per inch) monitors with varying artwork sizes. In particular, they mentioned Retina-class desktop and laptop monitors. @Stroughtonsmith tweeted from the talk which is not yet online:
We'd previously reported that Apple had also been planning for ultra high resolution Retina displays in Mac OS X Lion. These ultra-high resolution displays would increase the number of pixels per inch found on both laptop and desktop displays.
There's been some doubts about when such displays will become commercially available, but it seems both Apple and Microsoft have built in support for it in their latest operating systems. Microsoft seems to indicate that they will be available within the next couple of years.
Article Link: Microsoft Also Preparing for Desktop/Laptop Retina Displays