I really doubt that UE4 will get Mantle support anytime soon on PC.
Considering that PC version is focused on DirectX, and it’s not even using OpenGL to it’s full potential.
I think that migrating to OpenGL would be better in long run than to Mantle, as every vendor support OpenGL and it’s still evolving, which can not be said in case of Direct3D, which is not evolving, but sometimes make jumps, stop half in air, and fall down (;.
In anycase my point is that OpenGL gets access to new tech quicker and you can do now some amazing things with it, like unlimited textures per object (Bindless Textures) or MegaTextures (diffrent names for diffrent vendors but the idea is the same). Using either of tech could amazing for let’s say terrains.
But the true advantage os using those extensions, is that you can push thousands of textures in single draw call.
The problem is that UE4 is still targeting DirectX10 level hardware, this point is the thing that I really don’t understrand. By the time that first UE4 games will be released it all those GPUs will be ancient history.