They're not saying much, but hints suggest no. Not sure why, though - the last of the G4 iBooks are nearly identical to the PowerBooks they're supporting.
IIRC, only the very last model of the G4 iBook has USB driven touchpad, like the supported G4 PowerBooks. They might decide to support that one G4 iBook model, but probably not any of the other iBooks. Matt is right when he says that there is no word on this from the MorphOS Dev. Team.
I am hoping that the next version of MorphOS will be available before my trip to AmiWest this year, and that it will support the G4 PowerBooks at that time. We will just have to wait and see what is supported and when it the next release will arrive.