I would point out that X is still supported on macOS (via a community project, but still). OpenGL isn’t going to disappear.
macOS’s OpenGL has always lagged behind the latest versions of the standard anyway: the latest versions on Apple hardware are 3.3 and 4.1, released eight years ago. I think Apple made this decision a couple of years ago and just didn’t tell anyone.
It’s an unfortunate decision, and one that Kitware should open up with Apple as a vendor-to-vendor discussion, but this isn’t going to have a perceivable impact on our community for a while.
Would I start an OpenCL-dependent project right now? No, but that was an iffy gamble anyway.
—Mike