I was in charge of the hardware for a mid-sized design and video production shop from 2010 into 2015.
and as you mentioned, "18 core beasts". the needs of 3D/CG work (Max, Maya, Nuke...) has been out of the reach of Apple for some time now, especially when you want to build a render farm*. so yeah, I've been expecting the wholesale industry changeover to Windows for some time now. but people (myself included) are keeping those old Mac Pros (and even a few trash cans) on their desks, waiting and hoping. I guess we all find out by years end whether Apple cares as much as we do. it's a shame no journalist, columnist, blogger... that gets access to Apple's executive team will ask that one simple question re. the Mac Pro, what do they expect people to do?
* before anyone returns with, you can build a Mac Pro render farm... yes. but it's a terrible waste of space and money. and only very recently has any sort of final rendering taken advantage of GPU processing (and still a limited case tool), and then usually with Nvidia hardware. so the included GPUs are just a waste of money and electricity. the last render system I set up put 160 real cores and 512GB of RAM (across 8 systems) in 4U of rack space. just over $50K custom built. to get that much potential with Mac Pros, using the 12 core and racking it. At least double the cost and 7 times the real estate. no thanks.
We work in the same field.
I agree. No one in their right mind would consider building a render farm with Macs. Building a Mac based farm has never really been a realistic option. Ever. Apple simply never made an appropriate machine, including the Xserve. At best you see Mac's on the desktop talking to a server room filled with Linux or Windows blades. And with the rise of GPU rending the Mac is even less of an option. It's not uncommon to see dual or quad processor Xeon based Supermicro based servers stuffed with 8 or more Nvidia cards. Apple isn't even part of the conversation.
The closest I know of are a few small farms made with quad core i7 Mac Mini's. But I'm talking anywhere from 4 - 20 machines and they are used for things like AfterFX. They are in small shops or owned by individuals who are not technicians and just wanted something even they could maintain themselves, even it it was a more expensive option.
We saw an uptick with the cMP boxes a few years ago as workstations, but the nMP has not enjoyed anywhere near the same popularity. Editors bought the nMP, as did a lot of sound engineers, but they are nowhere as common as the cMP was. One post house i know of put considerable money into upgrading their 'ancient' cMP boxes rather than buying the nMP. Aside from the nMP being a dead end in terms of upgradeability, heat related GPU failure has been a common problem with the nMP and no one wants the aggravation or expense.