[someNameIG]

ARM would be a reasonable alternative. Unity/UE5 already support it due to mobile and Nintendo Switch, and consoles are usually more power/thermally constrained than desktops, so AMR in many ways would be a better alternative than x64.

Plus PlayStation is big enough that if they went ARM, game devs would have to follow.

[MBCook]

But were there fast/powerful enough ARM chips to be competitive with what ended up in the PS4/XBox One?

They certainly exist today. But could Sony and Microsoft have chosen them or would they have had to have them developed?

[someNameIG]

I'm not sure, the Jaguar CPUs in them were pretty underpowered at the time too, they were tablet/netbook level. I think they were in some ways a bit of a downgrade in CPU performance compared to the Cell in the PS3.

Biggest issue at the time would have been an ARM CPU with a decent GPU if they wanted a SoC instead of having them separate dies