This aspect is two-fold (at least). Yes, it's on the roadmap to implement OpenGL on Vulkan and probably also legacy-D3D on top of D3D-12. But what's more impor

This aspect is two-fold (at least). Yes, it's on the roadmap to implement OpenGL on Vulkan and probably also legacy-D3D on top of D3D-12. But what's more important is, that all the complexity of OpenGL and legacy-D3D drivers make it very difficult to hit the fast codepaths of the driver. And OpenGL has the problem that one cannot effectively queue drawing commands from several threads; not to be confused with the (ill) attempt to render from several threads at the same time. We're just talking about the preparation steps here, i.e. traversing the scene, visiting each element sorting them, and one drawing order is determined submitting them into a queue that then can be batched for drawing. With Vulkan one can utilize the multiple CPU cores we have these days: Each core may collect a different aspect of a scene into a different queue.