Hackintoshes will out sell Mac Pros in the future, as if they haven't been already.
...until MacOS
needs a T2 chip to boot and hacking one kernel module won't do it. Because security, you know. OK Apple has to support old hardware for 5 years, but they could tie support for up-to-date hardware to the T2 chip.
If Apple goes back to proprietary chipsets/hardware, then this will be a regression. Doesn't everyone remember what life was like before 2006? Apple moving to the Intel chips opened up the OS X development community to a broader market.
2006 was 12 years ago, and a lot has changed since then. Even MS is looking at full-blown Windows on the ARM - and their current development tools for C#/.net etc. target a virtual machine rather than bare X86. iOS development is probably bigger than MacOS development now, Android development - again, CPU agnostic. XCode/ObjC/Swift - all CPU independent and able to target ARM or x86.
(NB: I should be saying AMD64 not x86 now, too, lest we forget the delicious irony that Intel's 64 bit architecture flopped and they ended up adopting AMDs 64 bit extensions...).
Also remember that Apple's
main reason for going Intel was IBM and Motorola's failure to deliver laptop- and SFF-friendly versions of the PPC G5. Now, thanks to ARM's modular licensing model, Apple can effectively make its own bespoke CPUs - and (for much the same reasons mentioned above) ARM is also starting to break out of its mobile niche into server and workstation applications (of course, that's where they started out back when ARM stood for
Acorn RISC Machine - the original ARM kicked sand in the face of the contemporary Intel 286).
I think x86 could easily become a niche for the real pro video/3D/audio market since, even if Apple ported their pro tools, those people probably use a gazillion third-party plugins.