New 21.5-inch Retina 4K models expected.
Mac OS X Hacked Onto Intel's Sandy Bridge Platform
Unwilling to wait for Apple to make the move to Sandy Bridge, Hackintosh fans have already managed to successfully install Mac OS X Snow Leopard on systems with Sandy Bridge hardware. By using a patched Darwin kernel, users are able to bring Mac OS X to Sandy Bridge, although the technique is obviously officially unsupported and may result in system instability.
The good news is, we've already successfully installed Mac OS X Snow Leopard!
The bad news is, until Apple uses these CPUs, it's a bit of a science experiment, as you'll need to use a "patched" non-standard Darwin kernel in order to boot the system.