Beginning with the upcoming version of Apple's MacOS announced at WWDC, the company will no longer actively support OpenGL or OpenCL. Apple is encouraging game developers to use its own API, Metal, instead of OpenGL or its successor, Vulkan.
This doesn't mean that everything developed in OpenGL will suddenly stop working. However, once 10.14 Mojave is released, if something OpenGL-related does break, Apple will no longer support a fix unless it's a critical bug or security-related problem.
This is effectively the start of a tapering off of support for OpenGL, as Apple puts it:
"When a deprecation occurs, it's not an immediate end of life for the specified API. Instead, it is the beginning of a grace period for transitioning from that API and to newer and more modern replacements.
"Deprecated APIs typically remain present and usable in the system for a reasonable time past the release in which they were deprecated. However, active development on them ceases, and the APIs receive only minor changes to accommodate security patches or to fix other critical bugs. Deprecated APIs may be removed entirely from a future version of the operating system."
The Khronos Group, which maintains OpenGL and Vulkan, enabled Vulkan support on iOS devices earlier this year. The group continues to work toward enabling Vulkan code to be executed on major development platforms, including Apple platforms that use Metal.