ThinkSecret provides some minor notes on both PowerBook updates and PowerMac G5 2.0GHz Shipment dates.
One possibility introduced by ThinkSecret regarding the fluctuating G5 dates is that a large order from Virginia Tech may have bumped other orders later... however, no significant confirmation appears to be available. This would correlate with their previous report that educational institutions may be the first to see Dual 2.0GHz machines.
On PowerBooks, there are reports of unspecified delays into September, despite having been "ready to go" in August.