14 DAY TRIAL // The most recent evidence of Retina display Macs comes straight from Apple’s Messages application where developers have discovered an "@2x" suffix that indicates planned support for higher-resolution graphics.
The developer documentation for OS X Mountain Lion, which includes the Messages app, reveals that “The inclusion of the @2x modifier for the high-resolution image is new and lets the system know that the image is the high-resolution variant of the standard image.”
MacRumors points out that iOS developers can include high-resolution imagery designated by the "@2x" suffix to support the Retina display found on the iPhone 4, iPhone 4S, and the newest iPod touch players. The blog explains that Apple's plan is to make it easier for developers to jump to 2x the linear resolution, such as from 1440x900 to 2880x1800 pixels.