Trilarion: ...Anyway, wasn't Vulkan supposed to be the successor of OpenGL as platform independent layer?...
Panaias: Actually, Vulkan is not a "successor" to OpenGL (in that it wasn't made to replace OpenGL). It's a completely new technology that gives developers even more complex & low-level graphics functionalities. I've programmed lots of OpenGL in the past few years (for fun) and when I decided to look at the Vulkan APIs I was amazed by the huge differences (I was actually scared :) ).
No, vulkan essentially replaces opengl. Opengl is the old way of doing graphics. Using Opengl to load shaders was a hybrid world. Vulkan is the modern paradigm where the shader is the first class citizen. You are pretty much meant to use vulkan instead of opengl at this point, if you are doing new development. It's way of working mirrors the changes that went into directx12, (and the way apple's metal does things) but they decided to start over instead of trying to bolt more cruft onto opengl. (In the same way apple decided to build metal rather than rely on others to settle on a standard)
The transition will be annoying, but a world of vulkan + metal is not that different from the old world of direct3d and opengl; and actually because of the design similarities, it is easier and less error-prone to create wrappers that can map between the technologies. Where the old opengl and direct3d technologies relied on a lot of hard coded behavior and were organized in a rigid way that made a lot of default choices for developers, the new technologies are all about a set of standard ways to interact with the graphics hardware that lets the developers make all of those decisions.
Opengl killed itself a long time ago, we just have been relying on it for cross-platform because it was implemented in enough places.
From an old games perspective, just because opengl is deprecated doesn't mean its going anywhere soon. You'll still be able to run stuff for a while, hopefully long enough for wrappers to be good enough. And it's not like opengl has been receiving major updates on OSX as it is.
The latest spec is opengl 4.6 from 2017. Apple is still on opengl 4.1 from 2010. Oh, and just for fun, before version 4.6, the last opengl update is from 2014. So there hasn't even been much activity with the spec itself (of course how could there be - vendors like apple weren't updating to the new versions, and opengl tries to have some backwards compatibility through the extension mechanism!)
Edit: although I guess we still have pesky DX12 to deal with. Bah.