they could probably do a very, very smart move « environmentaly friendly etc. » sale a upgrade kit with a motherboard and processor that can be installed in apple store....
make it a 3000€ upgrade.... get back as much used intel xeon w motherboard for free to do warranty... no matter what they do with apple silicon the will keep pcie slot as it is an industry standard for expension, there is absolutely no work around in professional environment...
I highly doubt they will go over such a massive overhaul of the true macpro that they couldn’t upgrade just the mobo... building new tools to produce the exact same form factor computer makes no sense... no matter what they choose either they will reuse that chassis the way it is, or go back to a stupid trashcan /cube special proprietary design...
there is absolutely no desire from professionals to move away from the actual design which is almost perfect, just with a lame cpu .
they could totally build a 32 core macmini M1X that would obliterate any high end intel macpro, so the only reason of building a 8.1 is to keep the form factor and just replace motherboard and hardware with the same form factor.... there is so much power, space and slot in this design that they can do whatever they want with those cases...