The first signs of a new Intel-based Mac Pro have made their way online courtesy of an Xcode 13 beta. The first beta contains references to 3rd Generation Xeon Scalable Processors, server-grade CPUs based on Intel's Ice Lake architecture. Currently, these 10 nm processors are available with between 8 and 40 cores.
https://www.notebookcheck.net/Evidence-of-a-refreshed-Apple-Mac-Pro-with-Intel-Ice-Lake-processors-emerges.544549.0.html
Seriously, upgrading any MacPro at this stage in the transition to Apple custom silicon would appear to be utterly cynical. Also, Icelake is completely the wrong choice for the MacPro in any case and Apple by the time of any product release later in the year will already have a processor that can exceed the performance of every Icelake and Tiger Lake processor out there. So, this doesn't make a lot of sense on the face of it.
It wouldn't surprise me if what enventually transpires deviates from the detail of this speculative account. Apple, indeed, may have to ween MacPro users off Intel. I could see something with Intel inside that nonetheless aids the transition to Apple custom silicon by some means being on the cards though. I don't have a clear idea of what that would mean in practice.