I don't get why people would wait for the next chip. Apple is not guaranteed to put it in their machines on day one. They will wait for the market to demand it, for a drop off in sales. That won't take too long but we could be talking months....
Waiting when the release is imminent is one thing, when it could be a year away is another. Having said that, if your current PB is less than 18months old, then I can see why you would wait: because your not desperate for the new machine..