I got my 12" PowerBook G4 a few weeks after the current revision was announced (the 1.33GHz 12" and the 1.5GHz 15" and 17"), so I'm happy. But I probably won't when the next PowerBook revision comes out. And I'm only in 9th grade, so I'll probably have my 12" until university... It seems fast as **** now, but in 4 years that probably won't be true.
Yeah, the PowerBooks will probably be updated in a few weeks/months. If you really can't wait that long for a comp, get the 12" Powerbook/iBook now, they're fabulous machines, really. But if you really want the latest and greatest from everybody's favorite company, Apple Computers Inc, I'd say wait a few months until the newest revision comes out.
HOWEVER, one problem with getting the newest models is that all the bugs aren't worked out. The next 'Book revision will probably still be a G4 processor with the same look as the current 'Books, but when the G5 PowerBook comes out it might not be a good idea to buy it, because all the bugs aren't fully worked out. It might frequently overheat, the hinges might creak, a lot of bugs might not be worked out. It's usually better to wait 2-3 revisions after the original product is made.
Since the next revision will probably still be a G4 processor, chances are that the next revision will have smoothed out practically all of the bugs in the Aluminum G4 PowerBook model. So you'll be getting an excellent machine. So either buy now or wait a few months, whatever you prefer. You'll be happy either way.
Good luck!