For developers, there's another constraint in investing in the Mac Pro: the increasingly high likelihood Apple will move to ARM: > Mac Pro + display coming in at $11,000 a year or so before a switch to ARM is a hard nope from me. It's a little freeing, so I can now actually get a Mac mini https://twitter.com/stroughtonsmith/status/11356329822896537...
Also the idea that ARM hardware is somehow a threat to your "investment" is just random FUD. First, it's still just speculation. But second, assuming it's 100% true -- you're kidding yourselves if you think Apple is suddenly going to appear with magical Xeon-class 28-core ARM CPUs sometime in the next year that can compete with what they're offering here. Try 5+ years (minimum) after their first desktop-class CPUs are proven rock-solid. This Mac Pro cycle will probably last that long. If they do switch anytime soon, it will likely be only lower end machines like the MacBook Airs and non-Pro models. And even then, if history is anything to go by, they'll offer 5+ years of binary compatibility for newer devices to run old applications and multi-target toolchain support for developers to target all systems. People keep computers, even laptops, for longer and longer now. x86 macOS machines are not going anywhere, anytime soon, and Apple knows not to randomly segment/abandon users like that.
I'm not going to buy this machine for a number of reasons (including the astronomical base cost), but FUD about future magical ARM machines doesn't hold up at all, IMO.