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