This happened just minutes ago.While I do not have too many details otherwise, Crytek and AMD have announced that mainline CRYENGINE will support the Mantle graphics API. CRYENGINE, by Crytek, now sits alongside Frostbite, by Dice, and Nitrous, by Oxide Games, as engines which support that alternative to DirectX and OpenGL. This comes little more than a week after their announcement of native Linux support with their popular engine.
Here's an early article from PCper: http://www.pcper.com/news/General-Tech/GDC-14-CRYENGINE-Support-Mantle-AMD-Gets-Another-Endorsement
Exciting news indeed.