From what I understand Mantle is a "low level API"; lower than DirectX API. To put it simply, that means there are even fewer "layers" between Mantle and the actual hardware which technically allows more direct access to the actual hardware itself when developing a game than before.
Mantle is not a patch. So there will never be a "Mantle Patch" for games like Crysis 3, Battlefield 3, Hitman Absolution, The Sims 3, etc. The Mantle API is used during the development of the game itself.