My understanding is that Vulkan does NOT deprecate OpenGL, at least not for most use cases. Vulkan is a lower-level API that OpenGL can be implemented on top of, much like Gallium3D. As such, much development will continue in OGL, and only lower-level tuning will require the use of Vulkan.
> Vulkan is a lower-level API that OpenGL can be implemented on top of
Well you could do that, but the higher-level graphics APIs use fundamentally different abstractions which need to be awkwardly translated into a format that the GPU expects.
If you put an OpenGL wrapper on top of Vulkan, you lose most of the performance benefits.
> My understanding is that Vulkan does NOT deprecate OpenGL, at least not for most use cases.
It's clearly deprecate it in case of games and even more in the case of VR since you need high-end hardware that all support Vulkan.
For other games and low/middle-end hardware you simply don't want to use OpenGL for cross-platform game since it's total mess on Windows thanks for Intel, AMD and Microsoft. So it's only usable on Linux / OS X and this is why PC game developers don't use it.
Here's a lengthier discussion about it: https://forums.khronos.org/showthread.php/9717-Will-Vulkan-e...