As always Apple tries to bring water to his mill and starting from the next version of his MacOS, the Cupertino company has decided not to support more actively OpenGL and his successor Volcano.
To be specified that compatibility with products developed with OpenGL will be guaranteed.
On the other hand it is from the 1992 that this specification is on the market, so preventing the proper operation of products developed using this interface would be pure madness, but from the MacOS 10.14, "codenamed" Mojave, if something based on OpenGL should stop working or have problems, Apple it will no longer provide a direct fix unless you are faced with a security issue or a critical bug for the operating system itself.
With this move Apple he wanted to start a transition period at the end of which he would like to bring all the developers iOS to use the interface created by Apple same, from the name Metal.
Commercial move in line with the policies of Apple, but the developers iOS how will they react to this choice?