Everyone who doesn't develop exclusively for MacOS X, which is most of us. Am I going to rewrite my OpenGL application to use Metal. No. I might update it to

Everyone who doesn't develop exclusively for MacOS X, which is most of us. Am I going to rewrite my OpenGL application to use Metal. No. I might update it to use Vulkan, and see if it works with the MoltenVK shim for MacOS X. But I'm afraid that Metal itself is a complete non-starter.