It's been suggested and speculated by many for some time now. I don't think they'll be exactly the same, but the descriptions we've had of them sofar pretty much match.
Cell and XenonCPU the same? The article says nothing of the sort. Its says Cell's PPE is the same as Xenons, an in-order Power core. There the similarities end. XenonCPU doesn't have half a dozen cacheless assistant processing cores, nor a RAMBUS interface. Don't evenknow if XenonCPU uses dynamic logic either.
So short of sharing of sharing an ISA and both consiting of NOT, AND, OR and XOR logic gates, I don't see much similarity