I think the next iBook revision will have a 1Ghz Gobi G3 as the base configuration and an 1.25Ghz G3 as the top config...
but it's completly uncertain when this update will be (x-mas or january maybe..?)
IMO there won't be a G4 in the iBook ever (maybe the rumored mojave G3 that will be called G4+, but not a motorola G4)
vSpacken