CUDA 10.2 (Toolkit and NVIDIA driver) is the last release to support macOS for developing and running CUDA applications. Support for macOS will not be available starting with the next release of CUDA.
Say bye bye to CUDA.
The Mac Pro has got 7nm Vega GPUs which AMD themselves have end of lifed and not RDNA cards. The Mac Pro appears out of date before it even ships so there’s no link to the radio silence from Redshift and Otoy and no link to new RNDA 2.0. Apple won’t have any of the new RDNA 2.0 cards in Macs for many months, we know the Mac Pro won’t have them, if there’s an iMac refresh ready for release it at best will have a RDNA 1.0 GPU.
I suspect the reason you’ve heard nothing from Redshift and Octane is due to them having great difficulty in getting their renderers to work under Metal. One of the Redshift developers even admitted that Apple were doing a lot of the development. Metal and Prorender didn’t make any difference, Prorender in C4D on Mac was as dire as it ever was.
The more informed tech youtubers think AMD’s ray tracing may not feature dedicated hardware and be done with DXR and brute force. Many in the industry think fixed function hardware like RT cores is the wrong direction as it has no use other than ray tracing and programmers would much rather have masses more general compute to play with. RTX has been a complete failure in gaming and to make it work at frame rates gamers expect would require many more RT cores on the next GPU.