I am concerned by this since GPU acceleration on Mac is based on OpenCL which is a cross platform standard.
I have no inside information, but while Apple remains secretive about the details, its management has been sharing enough clues about their product plans that I think it's fairly evident what is going on here.
While in principle it's nice to have cross-platform APIs like OpenCL and OpenGL, they haven't been particularly successful in the respective markets that matter most to Microsoft and Apple. They apparently have been trouble-prone to code to (that's an impression; I have no personal experience using them) and their performance has been disappointing.
If you're a hard-core gamer, sucking down enough electricity to power a Las Vegas casino and running superheated, water-cooled graphics processors, chances are your applications were built on Microsoft's DirectX APIs. MS-Windows is the predominant platform for personal computer gaming and it's an important market for Microsoft. Not because there are so many gamers out there—although I gather there could be more of them than might be evident to old-timers like me—but because it drives a fast-moving, competitive, generic high-performance hardware industry that, in turn, generates the high margins that allow the same manufacturers to produce the
inexpensive generic hardware for institutional IT managers (such as I used to be) who acquire thousands of machines at a time for office workers and license MS-Office products to run on them.
Gaming has never been Apple's strength. Yes, some gaming developers used the open graphics libraries because they wanted to maintain a presence in the Apple ecosystem, but their applications were probably coded for DirectX on MS-Windows, so they were already in many cases supporting two different sets of APIs. Switching from OpenCL/GL to Apple's Metal will involve a one-time conversion effort. Assuming they want to do so.
Apple has a large installed base among home users and other individual buyers, but the company's primary
institutional target is the so-called multimedia market, and particularly the large commercial video shops. Apple has a strategic advantage there that it hasn't exploited very successfully in the last few years because of the amount of time it is taking the company to engineer a new product generation. In a Microsoft environment, it is necessary to push extra compute cycles through an inherently sludgy hardware abstraction layer, but Apple can couple the hardware and system software much more closely. That allows it to deliver high performance more efficiently—which is really important for large graphics shops, where power consumption and the concomitant need for air conditioning are serious cost factors—and offer developers the hooks they need to exploit that efficiency with minimal programming effort.
So in the Microsoft universe, you get high performance hardware at a premium price and operating cost for power users, and inexpensive hardware for institutional office customers. In the Apple universe, you get an easy-to-use ecosystem of desktop, portable and mobile devices for individual users at a mid-range to upper price-point and—potentially, at least—a very efficient platform for institutional graphics customers.
So where does that leave the majority of
us (i.e., LuLa forum participants), who, I presume, are primarily interested in post-processing stills?
Well, my 2013 Mac Pro (six cores, 64 GB of memory, 1 TB flash filesystem) is still a very capable platform for the two photography apps I use the most, Lightroom and Photoshop, and I expect it to remain so for several years to come. I don't use more specialized applications like PTGui, but I presume they would perform even better on MS-Windows with the DirectX APIs and even better on MacOS with the Metal APIs—and Apple isn't
ending support for the cross-platform graphics libraries, just alerting developers that it's time to start planning for the transition.
Frankly, unless you have a strong preference for one operating system over another, or do your own software development, I don't see why it matters to most photographers which operating system they use. The applications that support both operating systems mostly look and work the same on either platform.
I think Apple understands that some customers feel constrained by the hardware performance of their current products—hence the iMac Pro—but those who really need the highest level of personal computing performance, or at least believe they do, can easily assemble a very powerful machine from generic parts (or buy one from an integrator) and run MS-Windows on it. Or wait another year for Apple to roll out its next generation of products, and see if the company can successfully exploit its strategic advantage as the designer of integrated hardware and system software.