Thanks for the great info Jaymie (@jstrecker)! As always it looks like Apple has pressed fast forward on the EOL of OpenGL. Hopefully it will be positive for the industry, and for Vulkan (which didn't look like it was gaining traction on MacOS). All I know about Vulkan vs OpenGL is that it's very different, very low level, and not always faster (for high resolution outputs no; but for 1080 much faster).
(When looking at game benchmarks etc)
UPDATE: Just been playing with the 'Vulkan Traiangle' tutorials... looks like I am wrong, and Vulkan can swap out shaders on the fly, (at least if I recompile the shaders obviously...) Having a default way to compile shaders (with error feedback) is a nice change to the silence that was GLSL.
The way I understand Vulkan & Metal is that GPGPU is built in directly into the standard- as opposed to using an additional standard.
I am also very concerned. OpenGL isn't going anywhere soon, as Vulkan is still actively developed. There are many titles that are cross-platform and rely on OpenGL to make this all work.
In theory simply the OS not using OpenGL shouldn't stop it from working. However if Apple take measures to actively remove support (libraries etc) then possibly a 3rd party solution could keep it alive? (Linux has MESA etc, maybe this could be used as a starting point)
Just another thought, it would be great to be able to also disable window shadows. I know that there is software that can switch this off universally on MacOS- but if we distribute an app it would be cool to be able to control this behaviour.
I can see this being very useful for screen overlays, or non-interactive screen modifiers.