Lets edit my post here and put 1,67 ghz in ibook will hurt powerbook sales.
Macmini will get minor bump, but I doubt it will get 1.67 ghz unless Apple is sitting on huge supplies or still has on order with Freescale.
1.67ghz in the mini or ibook WON'T happen, because the powerbook is at 1.67 ghz. Unless Powerbooks are updated with a minor speed bump to 1.8ghz. If it does happen, Powerbook sales will fall.
The mini is built for switchers, to surf the net and listen to music and , not for high end professionals.
Wait a week or two to see if these rumors about the ibooks are true and then go for the iBook if its updated.
If they are not updated, go for them anyway and with the price difference between 14" ibook an 17" Powerbook, go get yourself or wife or family a nice gift.