If they abandon "Pro" niche more power to them - but we are discussing a potential "Mac Pro" workstation in a "Mac Pro" threat so let's stick to that. So, it's either a Mac Pro workstation or a subject to ridicule, which it will be if they deliver it in closed architecture form factor. I don't see them opening it and embracing 3rd party GPUs - it would be against everything else they do at this point. If they do that I will be positively surprised and happy to buy it. Other option is creating their own standalone GPUs but lets face it - noone in the right mind would go that route for a niche product that constitutes 0.02% total product sale of the company

I think we can agree that without real GPU power, this Mac Pro would not be well suited for any visual work in 2-3 years - not only because of no 3D capability but also because of weak support of all the upcoming AI tools we will get in Adobe Creative Suite etc (there is NO other route of development for software companies - they have to embrace AI tools or become obsolete, and I'm not talking about stable diffusion but more about generative, procedural AI tools like the nVidia tools for game devs, AI up-resing, denoising, all the AI stuff you can do with motion picture which is a separate matter, etc etc).
So to sum up there is only one way - 2024 Mac Studio M3. And that should be it. No real R&D cost on Apple side, its sufficient for *some* Pro applications and all the rest will have to switch to Intel/nVidia combos.