The i9 is likely to replace the Xeon at the very least. The i9s are 6 core CPUs, so you can see a 12 core MacPro coming in the near future.
I'm hoping for the PA Semi 6T and POWER7, MUCH more powerful than intel offerings, or an addition of AMD to the line
no doubt, the release will cost big buck and then taper off as usual, but the xeon 5500 is the front line technology right now for us simple folk, are the "i" chips that much more of a big deal. From what Ive read whats out there right now is more then most people even need, even the techies in the intel forums are more than happy with the nahelem technology....