Yesterday Apple released a developer preview build of OS X 10.8.3 to its testing community, and upon investigating the build a few people have found it includes new drivers for AMD's high-end Radeon 7000 series graphics cards. People who have tested the build with PC versions of the Radeon 7970 have found that the card is recognized and works, and suggests that possibilities for new hardware offerings from Apple are in the works.
In the past, Apple has switched back and forth between graphics processors from AMD and Nvidia with iterations of its hardware, with its latest systems primarily shipping with Nvidia hardware. The exception to this is Apple's Mac Pro lineup, which comes with the Radeon HD 5770 by default.
With evidence of support for the Radeon 7000, Apple may be again gearing up to switch some of its systems with built-in graphics (iMac and MacBook models) to AMD graphics, but more likely Apple may have an update for the Mac Pro in the works.
There is no doubt that the Mac Pro is perhaps the least popular of Apple's Mac offerings, and given Apple's focus on its mobile products, the Mac Pro has quite obviously been put on a back burner; however, it still has a niche market among creative and technical professionals who need raw power, and Apple is providing support for new graphics options.
Some have suggested that the Mac Pro may be in the midst of suffering the same fate as the XServe; however, Apple CEO Tim Cook has, stating that Apple is "working on something really great for later next year" with respect to the Mac Pro.
While new support for a high-end GPUs may only accompany changes to Apple's CTO offerings in the Apple store for current Mac Pro models instead of suggesting all new Mac Pros are around the corner, it does suggest the company is keeping the Mac Pro around. Support for the new GPUs also suggests that current Mac Pro owners will be able to upgrade their graphics to take advantage of the latest offerings from AMD.