I'm pretty sure the PBs and iMacs will go G5 nearly at the same time. Because once they fit the G5 into a PB, it'd be easy to do so in an iMac. ...Maybe a new iMac formfactor? I could see that as an explanation for the wait. As for the powerbooks... waiting for a cooling tech to use? Cause God-forbid that mac users have to deal PC laptop typical heat from their laptop.
...maybe people are getting the idea that arguing against comparisons like that is just a complete waste of time?