Seriously?! How can anyone who knows their tech say this, especially after seeing what the Cell can do? I mean, just look at Uncharted's or Max Payne 3's animation system and try to tell me that CPU's don't matter.
Cell is a completely different beast though. Most of its merits lay in its specialized design thar allows it to aid/compensate the GPU with many operations. When designing a new console with hardware available today, no engineer would consider spending silicon in that way again, but rather spend it on the GPU where it belongs. Seeing how the PS3 lasted with only one PPE (that's not the whole story though I admit) should be an indicator of how little general purpose processing actually matters.
I'm not advocating to completely nerf the CPUs, but it makes no sense to invest in them over the GPU if they are 'fast enough'. Which probably can be achieved by rather simple designs already. Let me rephrase what I said: general purpose processing should be of surprisingly low priority in the design of the next Xbox's chip.