I'm not going to answer this question until we get more details or until we see a new iBook. The new iBook, in my eyes, will see a processor bump to 1.42 GHz (1.5 GHz at the very most,) a graphics card bump, maybe minimum RAM to 512 MB, and who knows about the widescreen rumor. I think Apple's consumer thing here is to beef up the processor slightly, a better graphics card, 512 MB RAM, and Bluetooth all at the same price. At least that's what they did with the iMac in May.
So, if I were you, wait until they update the iBook, see what happens there, and if you don't like what you see, get a PowerBook. (The other thing about the PowerBook is that there aren't any rumors going on about it and I'm guessing it won't be seeing an update until the holiday season.)