There will be two models of Mac Pro? I would love for that to be so, basically sell both a cMP and a nMP. But I don't think Apple will do it.
Let's not say "cMP" and "nMP" in this context. One doesn't have to be a "new cheesegrater", and the other doesn't need to be a "new trashcan". And why not three models - small form factor (SFF), mid-tower, and large tower.
Many people love the nMP because it's quiet and small. The SFF mMP is the "Mac Mini Pro" - no hardware needs to be shared with the nMP or mMP (and hopefully that gawd-awful thermal core idea is sent to the bottom of the ocean).
The SFF is the xMac. albeit with external expansion. Much cheaper, because it will be single GPU in the base config, Core i7 (or whatever is current at the time that it ships). Probably doesn't need more than one standard PCIe slot.
The mid-tower is single socket with 12 DIMM slots. Four PCIe slots, supporting dual SLI (double spaced slots - no slot wasted because of wide GPUs). Nice rack of ports, 4 to 6 NVMe SSD slots, and three or four 3.5" spinner slots.
The large tower takes the mid-tower motherboard, and connects an expansion board to the QPI with a second socket, 12 more DIMM slots, 40 more lanes of PCIe.
This is more or less what you can buy today from HP/Dell/Lenovo/Supermicro/.... (Although I don't think any of them put the second socket on an expansion board anymore.)