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 don't think "deprecated" is the right terminology here. Nowhere on the Khronos Group website can I find a statement that OpenGL is considered deprecated. Not on the landing page for OpenGL (https://www.khronos.org/api/opengl) and not in the OpenGL FAQ (https://www.khronos.org/opengl/wiki/FAQ).
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.
But, Python is not gone. There is a new version, I can still use the next version of Python. Like you said, OpenGL does have an upgrade path to Vulkan.
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.
Vulkan is a totally different API from OpenGL. It's not hardly a mere name change and the initial work that became Vulkan originated outside of Kronos anyway. There is no "upgrade path" from OpenGL to Vulkan short of a total rewrite. This wasn't done maliciously or carelessly; the two APIs target fundamentally different abstract models of how graphics hardware works.
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.