PS4 offers OpenGL but AFAIK that will only be used for x-platform games where performance isn't crucial, e.g. indies, or possibly for parts of the rendering pipeline where OpenGL is just more convenient and already fast enough... therefore having a speed-up to OpenGL is just not relevant to AAA games. MAAAYBE it could expand the amount of work that can be done via OpenGL with less down-and-dirty GNM Sony API work, thusly making development easier and freeing resources for other things, but that code isn't really going to be faster than what GNM could accomplish. This is exactly why AMD themself say Mantle is irrelevant to PS4, it's native API already allows what Mantle does.