I have no insider info, but be realistic. The iBook will see faster G3 chips, maybe some better graphics and battery power, and maybe a minor update to the case to make it more durable. Other than that, the only thing to change is a drop in price, which is already fairly low.
Frankly I think built in Bluetooth and Airport should be standard across the line, consumer and pro, portable and desktop, but they may hold out on the iBooks. Firewire 800 on an iBook? Don't make me laugh?
What the heck peripherals do 99.999% of current or future iBook owners have that either have Firewire 800 or would greatly benefit from it? DV editing on an iBook is .... not my idea of a good time!
I say keep the G3 iBook around, and make them as cheap as possible. Anyone who wants a REAL laptop will get one of the new Powerbooks. The iBooks are for kids, students, very non-demanding consumers, and maybe as a basic secondary or tertiary machine. And they fill this niche VERY well.
That said, itd be interesting to see them add that color-changing case stuff to an iBook. Might be too expensive for it, but imagine a glowing pink iBook for little Susie, or a nice blacklight one for Faruzia, or a rainbow one for Graham Norton?