I'm curious what leads you to believe that support for OpenCL is waning. From what I can figure, most graphics developers didn't care for CL much due to clumsy interop with GL, which is why compute was added directly to GL core in 4.5. It's much more useful to game/graphics developers in that format than CL is, and CL has moved to more scientific computing type uses. I don't think Vulkan plays in at all.
Yah, I've only seen OpenCL and the like used for simulation/neural network/etc. stuff. Graphics tend to stick with whatever's native as possible.