Mojave only deprecates OpenGL, but it doesn't remove it as far as I understand. It will continue to ship with the (somewhat outdated) OpenGL version that macOS has provided for several years, no? Did they even try running their own product on the Mojave betas? Seems strange to discontinue a working product just because an API is marked "deprecated"?
I've been building and running OpenGL toy applications[0] on Mojave public betas without issue just to check on that. You just get lots of deprecation warnings at compile time that you can quench by defining GL_SILENCE_DEPRECATION. Excerpt:
./nsopengl_example.h:5:5: warning: 'NSOpenGLContext' is deprecated: first
deprecated in macOS 10.14 - Please use Metal or MetalKit.
[-Wdeprecated-declarations]
NSOpenGLContext* _openGLContext;
^
/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/System/Library/Frameworks/AppKit.framework/Headers/NSOpenGL.h:202:12: note:
'NSOpenGLContext' has been explicitly marked deprecated here
@interface NSOpenGLContext : NSObject <NSLocking>
^
nsopengl_example.m:97:9: warning: 'glVertex3f' is deprecated: first deprecated
in macOS 10.14 - OpenGL API deprecated. (Define GL_SILENCE_DEPRECATION to
silence these warnings) [-Wdeprecated-declarations]
glVertex3f( 0.0, 0.6, 0.0);
^
Nothing is gone yet.
I suspect they'll proceed in a similar way as with OpenSSL, first deprecate, then remove headers, and keep the libs around for quite some time for legacy applications. In Mojave public beta /usr/lib still contains libssl.0.9.7.dylib and libssl.0.9.8.dylib, and it's been quite some time (El Capitan [1]) since you haven't been able to build against them.
The trickier part with OpenGL though is the graphic drivers. I suppose at some point in the future drivers for fresh new GPUs won't include OpenGL support. Maybe they'll include a GL-to-Metal akin to MoltenGL in that case, maybe not, or a third-party will create just that to run legacy applications. Anyway I bet it's a long road ahead and won't happen overnight.
Apple have announced plans to deprecate OpenGL. Whether they do it next year or in three years the writing is still on the wall, and I can't blame any company that doesn't want to invest their time and money on a platform that'll be a dead end. Even if it isn't removed yet it presumably won't be getting updates that other platforms will.
(Plus, Autodesk might be trying to convince Apple to change their minds with a move like this)
Companies buying this type of software will often spend >$100k on licensing and support, and they don't want to add unnecessary risk by relying on deprecated and unsupported features.
Often the vendor will have a list of supported workstations, and the the customer will just buy systems from the list.
