Harlety Charlton at MacRumors has an article, “Apple Silicon Mac Pro Configurations: Everything We Know.”
Of course we don’t really know anything, other then it is coming, so it is literally all speculation. We think it will be based on the M2, and it might be 5nm or even 3nm, and we don’t know ports and it is rumored to have 40 cores, or double the M1 Ultra.
I wish this machine was a known quantity as it really should be my next machine if it isn’t too expensive.