Maybe we'll see a new 'large' iMac if/when there's something better than a warmed-over version of the 2017 5k panel to put in it. I mean, its great that the 2017 panel is still so good 5 years later, but I don't see it staying top of the heap much longer and wouldn't want to have one welded into a new computer today.
5k iMac is actually from 2014, so 9 years and counting...
As this is a what if thread, what if Apple just released OSX with support for existing or new PC based hardware so people could build there own Mac pro to the spec's they wish. OSX pro to support Nvidia or AMD GPU's and also intel or AMD CPU's much like windows.
if they were to do this it would attract at least 30% of windows user's to Mac OSX and most likely lead to more ipad and phone sales as people would take to the all Apple syndrome and most likely increase apples base of Ipad, mac book sales. It would also give software developer's an opportunity to develop more OSX based software knowing it wasn't such a limited market any more for pro user's.
This would also release Apple from R&D in the Mac pro space and concentrate on its hardware for Mac book pro's and Ipad revision's using AS.
Even charge for Mac OSX pro like windows. then people can upgrade as and when they want to hardware they can afford. This change alone would attract so many windows user's to OSX and developers.
No matter what apple release in the Pro hardware it's already out of date by release.
That'd be super cool. And, I'm 100% sure they have it running internally. When NeXT did a reverse-takeover of Apple -- I meant to say got acquired -- NeXTSTEP was running on its native 68K hardware, Sun SPARC and Intel (with an assortment of "NeXTSTEP compliant" configs, including the Dell DGX "Jaws" system they used to develop x86 NS). I seem to recall HP snakes and PA-RISC support, but never used that box personally, I don't remember if they had it running, had it in alpha or beta, or just announced it, and can't be bothered to look it up 🤷♂️
When Rhapsody was becoming OS/X, they had red box, which ran on Intel. They killed it, as well as Steve killing off all the Mac clones (all of which was a good idea, hindsight being 20/20). They also kept it all going internally, which made the Motorola to Intel transition a lot simpler for Apple.
Having said that, the odds of Apple selling its OS are roughly 0. I happen to agree with you, it's not the late 90s anymore, Apple has near-infinite runway to experiment, survive, and reinvent itself instead of stagnating, and they have an entire ecosystem of far more important products like all the iCrap & Services.
But, I don't really see macOS ever being decoupled from Apple's absolute control. That's kinda their thing. Hackintosh probably unsuitable for any professional environment.
As far as this whole thread goes, ya... when I got the MP 2019, my overall thoughts were, cool... all set for another decade I guess. Beautiful piece of over-engineered Heavy Metal sculpture. It makes me happy, that's priceless.
Happy New Year to everybody (in a few hours over where I'm at). Here's hoping Apple sprinkles magical and revolutionary pixie dust all over everything and kicks a new MP out the door with eleventeen slots, infinite RAM, Nvidia support, and anti-gravity pads instead of wheels. I'll start holding my breath.
p.s., my sig is like 10 years old, I was complaining about the lack of updated Mac Pro, with absolutely no idea it'd take another 7-8 years for next cheesegrater. This conversation is eternal. Apple always does this, or to be more accurate we're at year 15+ of Apple taking a completely schizophrenic approach to are, or are we not, making high-end workstations? And if so, how?
Cheers!
But for the context of a Mac Pro, sure. I think this is a key reason as to why the M2 Extreme is rumored to be scrapped. 
