Matthew Rothenberg writes in an eWeek article that the 1 GHz PowerMacs are only the tip of the iceburg:
Multiple eyewitnesses insist that Apple is far along in the development of new towers that already offer clock speeds in the neighborhood of 1.6GHz and triple the performance of the current systems' 133MHz system bus. My sources say the tangible boosts in graphics performance and Mac OS X speeds are immense.
