Sony never really hyped Cell. It was more of a PS2 scenario where others did all the hyping, but Sony never really denied it, so Sony get the blame. They say 'oh, yeah, aiming for 1TFLOP performance' (or something similar), and suddenly every Sony fanboy on the planet starts hyping it up that it's a supercomputer-on-a-chip with the ability to fly and cure cancer. At the end of the day, it's still a microprocessor, and has to operate in the same or a very similar way to every other microprocessor on the planet.
Also, IBM never confirmed that they would be using the same CPU for both. That was a rumour. All I know is that if I was a Sony or Toshiba, I'd be pretty pissed off to be paying IBM billions of dollars to 'make' a CPU that they already had! Not to mention that the 'rumour' has already propogated all over the internet, so if it were true Sony would know it by now. Oh, and on top of that, Sony and Toshiba both manufacture their own microprocessors and have been closely involved with Cell production, so they'd have to be pretty thick not to notice that it wasn't just the PPC architecture (you know, what with them helping to design it).
Until we hear further news on Cell, I don't think it's correct to assume that it will even use PPC cores, let alone that it's an identical chip to the Xenon.