[roberts]

Hardware has to come out first --> Operating systems catch up --> Host DAW s/w catches up --> Plug-ins catch up. This cycle at best represents 18 - 24 months of development. For example my Stylus was just updated I think my last update was 2006 - that's nearly 3 years!!! Many plug-ins still do not seem to handle multiprocessors to well. ( a few IK Multimedia Plugins).
Plus is you read about the new intel processors the second and 3rd generation will be a lot faster. I would what Snow Leopard is coming plus PT will need to updated and all the Plug-ins. You will not be able to take 'full' advantage until the whole cycle is done. And by then there will be new machines. Anyone who bought a 8 core last year should wait until at least 3 years before updating.
I know several people with HD still on G4's.
Always remember if you want to be a pioneer your are going to have pay extra for that.