Apple has priced the MPX W6900 ($6K ) higher than a MPX W6800 Duo ($5K). Both use the same fundamental die from AMD. So two dies are less than one (albeit better binned) die.
A 7900 replacement at the same price point would have a very similar ( so expensive ... how many folks are really going to buy it ) problem as the $10K M2 Extreme SoC.
Apple and AMD collaboratively worked on AMD GPU generational drivers when Apple both 2-3M AMD GPUs for iMac and MBP 15" per year. That volume to amortize development costs over is gone. That was being used to help defray the costs of the $2-6K GPUs for the 2019 Mac Pro driver development. When the Mac Pro has to pay for it all with only maybe 3 MPX modules the costs are going to go down? Probably not.
If the vast majority of end users bypass the MPX W7900 for the low cost, off-the-shelf version there is substantially even
less money to pay for the driver work.
This story about "too few users to sell to leads to Apple not interested in making a product" impacts the high end GPU space also.
With the used GPU glut sales of W6800 and W6900 are likely falling pretty fast. That really doesn't do much to 'enable' a next generation for Apple. The MP 2019 user base likely isn't getting substantively bigger. (if leave the core system with a 3 year old CPU ... how is that competitive with 2023 workstation offerings coming from Intel/AMD? )
The Mac Pro was far more dependent upon the rest of the Mac market to help manage kernel/driver/software costs than most folks want to admit. The 580X , W5700X , 5500X all had placements in other Macs (iMac , MBP dGPU).
Not sure why AMD would be jumping up and down at opportunity window of selling another 10-30K units when they are shooting for 100's of thousands per quarter.
The more the merrier!
www.tomshardware.com
The price points that Apple is selling at and the numbers likely to drive via Mac Pro sales might make some noticable impact on MI210 or future MI300 series cards. AMD position in the GPU market is not what it was back in 2016-2018. They don't really need for Apple to step in and sell GPU chips they can't sell elsewhere. Even more so to an Apple that would be buying in sub 25K/quarter volume rates. Buying another 20K/quarter MI210 might.
Pretty good chance that folks with a MP 2019 system that want a 7900 will do the same thing that the folks who wanted to run a 3090 30-70% of the time did. Boot the Intel system over into Windows and use the drivers there. Costs AMD/Nvidia/Apple an additional approximately nothing. Certainly what the hackintosh folks are doing.