Some misinformation in that thread.
IBM won the contract for the brains behind the PS3, which means it will be built on a PPC core. They're going for a heavily parallel approach that has been discussed for some time.
It's being called cell computing and I believe our Hannibal is preparing an article on the approach. Basically, the unit will have multiple "cells", each with its own vector processors (rumors I've seen say 8 per cell) and a core processor, all working together or on individual tasks simultaneously.
I have heard the 4GHz rumor but I believe it first came from the Inquirer which is less than reliable. I'd hold off on quoting details like that until more information is available.
BTW, you can learn all kinds of cool things about processors here:
http://arstechnica.com/cpu/index.html