AMD has reportedly "thrown all of their weight behind Vulkan and DirectX 12, telling developers that future games should use those APIs and not Mantle." Vulkan is essentially the rebirth of OpenGL and was actually initially called the "next generation OpenGL initiative" at one point. Valve has thrown their support for Vulkan with Source 2. DirectX 12 is the obvious big dog here and will be included in Windows 10.
The situation then is that in discussing the performance results of the R9 Fury X with Mantle, AMD has confirmed that while they are not outright dropping Mantle support, they have ceased all further Mantle optimization. Of particular note, the Mantle driver has not been optimized at all for GCN 1.2, which includes not just R9 Fury X, but R9 285, R9 380, and the Carrizo APU as well. Mantle titles will probably still work on these products – and for the record we can’t get Civilization: Beyond Earth to play nicely with the R9 285 via Mantle – but performance is another matter. Mantle is essentially deprecated at this point, and while AMD isn’t going out of their way to break backwards compatibility they aren’t going to put resources into helping it either. The experiment that is Mantle has come to an end.
Each of these APIs are meant to cut out a lot of the extra middle steps when rendering graphics. To put it simply, these APIs will help boost performance for your games on your existing hardware, provided the developers make use of those features in Vulkan or DirectX 12. The big benefits will really be seen by those with somewhat older hardware where the GPU is powerful but the CPU is lacking.
