By the very Khronos Group you mentioned. They are developing Vulkan now, which they consider the successor to OpenGL. There will be no new OpenGL versions, again it is deprecated technology. Deprecated by its creators just like Python 2.
And just like Python 2, you can still use it, but again it would be a questionable choice for a new project in both cases, and for the same reason.
I think the term "deprecate" implies some level of actively discouraging use that is simply not happening with OpenGL (and that was/is for sure happening with Python 2). Specific platform vendors may deprecate OpenGL on their platform (as notably Apple has done), but that does not mean OpenGL is deprecated by Khronos Group.
It isn't like because Python 2 was depreciated, you have to switch to C#. It isn't gone. You can use the new version. Or older version until ready to migrate. Maybe it seems like it because of a name change, and you don't want to call Vulkan, OpenGL
So why give up on OpenGL altogether, when there is continuing development.
Going from Python 2 to 3 wasn't a cake walk. Hence so many years to migrate.
But I get what you are saying. Some upgrade paths are easier/harder than others.
Yes, even despite of many similarities and shared stuff, which can't really be said about OpenGL and Vulkan.