Anything that isn't a Hollywood studio will have to use an ARM iMac.
Enthousiasts and semi-pro's that want a powerful, affordable and extensible Mac with state of the art discrete GPU's can probably get lost, as is the case right now.
Then again, Apple is now only bound by their own operations, so who knows what they have planned.
Now, it turns out that Apple wants to complete a transition in 2 years... they are not keeping x86 around for the Mac Pro longer than that. It's not credible that Apple can just scale up their CPU into a workstation part. So if you are making pro software then you have to come to the inescapable conclusion that Apple is, in fact, not serious about the Pro market, and it's probably best to avoid expending further development resources on the Mac.
Also crucially, due to Apple's spat with NVIDIA, the Mac Pro doesn't support CUDA. This means software has to be modified to use Metal Compute to support the Mac Pro.
If you make pro software Apple just let off a huge signal that the future of the Mac Pro is at best uncertain. So maybe hold off on that Mac support for the next two years.
Apple is not going to make an ARM Xeon. The resulting computer would be so expensive after you amortise all the R&D to create a single workstation class CPU for it, that nobody would be able to afford it. All the Pros who bought Mac Pro got played hard.