I think the next revision may entail a speed bump to 1.1 GHz (Gobi). I'm hoping for DDR support (supported by the processor) and PC2100, with PC2700 and PC3200 going into the PowerBooks. The increase of L2 cache from 512K to 1024K will offer improvement, and I'd imagine there will be an improved graphics chipset.
I doubt that the iBook will be EOLed. The iBook is a great deal and Apple can make it an even better deal by improving the architecture. If they use a chip that adds Altivec in the future, that will make the iBook an even stronger entry.
For now, unless IBM gets way ahead on the G5 at 90nm (and they're not), I expect a revision of the PowerBook to maybe 1.25GHz and 1.33GHz using the 7457 (if delivered). The 7457 offers some benefits over its predecessor, including an increased L2 (from 256 to 512) and, maybe, true DDR support for Apple. If the PBs cannot get DDR support then we won't see it in the iBooks. I'm hoping for a 200MHZ FSB int he PBs (a 167 in the iBooks) configurable with PC2700 in the 12" and 15", and PC3200 on the 17" and high-end 15" @ 1.33. It would be nice to see 1MB of L3 on the low-end models and 2MB of L3 on the high-end, but I'm not holding my breath due to the size of the laptops and the cost of L3.
Whenever the iBook gets Altivec, I can see it also having a Superdrive option - giving Apple the ability to put a Superdrive in any model in its whole lineup.
With any luck PowerBook G5s will come in March, possibly introduced @ MWSF. This will allow for introduction of a G4+ (based on improved G3 architecture) from IBM that will power the iBooks, eMacs, and low-end iMacs. I would hope that we see the G5 come to the iMac by March as well. It would also be wonderful to have a headless iMac that can be purchased in a variety of configurations.
And if IBM stays on time, I wouldn't be surprised to see dual-3GHZ PowerMacs out in March. I think most of the Apple line will get some minor bumps next month (eMac, iMac, Powerbook, and, maybe, the iBook to 1GHZ), but that a whole new lineup could be introduced at MWSF with several redesigns that will set the stage for the future of the platform. Probably just a pipedream, but it's be wonderful to see.