I think Apple will continue its partnership with AMD.
7,1 was an important release for Apple because, for the first time in virtually forever, they were offering graphics that were at least on par with the competitions highest-end.
Did they. The base GPU card the MP 2019 shipped with was a 580X. "on par" with the latest Nvidia offerings in late 2019? Similar the Pro Vega II was about 6 months before the Nvida A100 and the RX 8000 was shipping ( along with 2080Ti).
They had the top of AMD's class. But AMD class was not exactly timely.
If Apple were to not allow future AMD cards to be supported, then all I can say is that they must have a lot of confidence in Apple Silicon thus and their ability to at least match current performance levels.
Apple isn't trying to 'at least match' on every feature. The Mini's are still short or what an Intel Mini can do with max RAM capacity. All Apple has to do is sell GPUs with enough performance range to sell enough systems to make a profit. According to Apple the most highly bought configuration choices for Mac Pro major components was 16 core CPU and W5700 GPU.
Apple doesn't have to cover every fringe user. They just need to cover a large enough user base to be viable.
If Apple could do W6800 performance for $1-2K less money, then they probably would have a decent number of buyers.
The other issue is the presumption is that Apple is calling all the shots here. AMD may not be interested. They are not the "will they go almost bankrupt again' vendor they were in 2017=2019 era. Apple has dumped AMD discrete GPU from every other Mac system base configuration. ( number of GPUs they are buying has probably dropped at least one , if not two, orders of magnitude). Mac Pro and perhaps whatever eGPU can wrangle out of rest of mac line up with far more completitive iGPUs amounts to what? AMD has other projects where the main system vendor is not trying to put them out of business.
If they could not do this, it would be an embarrassing admission and a major step backwards.
Apple never gave themselves that objective. They mentioned wanting to have the fastest iGPU out of everyone. But building a 7900XTX or 4090 'killer', that has never aligned with any of the primary objectives Apple has laid out in any of the M1 or M2 SoC package introductions at all.
Further, continuing to offer MPX modules would benefit both the AS and Intel install base, which is more profit for Apple.
The Apple Silocon system needs a MPX module like another 'hole in the head'. The system thunderbolt ports will extremely likely be powered by the iGPU. If the base iGPU is the "M2 Ultra" class GPU, they are 'underpowered' how?
Most of the MPX complexity is about provisioning Thunderbolt both to the system's 4 ports and to the card's edge ports. The card edge ports are not really needed if just take an off-the-shelf reference card (to lower cost for system qualification to a minimum amount).
As for 'growing the Intel Mac Pro installed base'. Really? Most likely the Intel Mac Pro will be kept around for a while only because some folks are going to scoff at the new Mac Pro limits on modularity (e.g., RAM ) and very conservative software stacks that aren't going to transition over to M-series well. That isn't going to be a 'high growth' user base. If they are 'stuck' with 'buy the old one' option, then that is probably it.
Apple will probably not drop macOS upgrades for the Intel Mac Pro for several years ( 4+) , but lots of 'new' hardware features? Probably not.
