That would make things interesting. AMD & Sony vs Intel/Nvidia & Microsoft. It would push all companies to be more innovative.
This is what makes each new gen so exciting. Who will team with Who, and what new tech will we see from those collaborations.
I would actually like to see this happen. I think it would be healthy for the industry. It would be really interesting to see how a PS5 Pro and XB4 X turn out if all parties step up their respective game.
MS could also through in a Tegra based XB4 Mobile, while Sony delivers a Ryzen + Navi Mobile power PS5 Mobile. That would make things even more interesting.
Can't wait to see things for next gen unfold, no matter how it plays out. New gens, and new hardware, are always fun.
Nintendo using Nvidia Tegra X1 chip also makes it interesting. I'm assuming you accidentally left them out. This means two of the big three would be aligning with Nvidia.