To add on to my prediction, it will also have the Scrolling Trackpad and possibly the Sudden Motion Sensor and the 8x SuperDrive.
Even if they make the current GFX work for Tiger, I still hope they update it
Considering that Tiger will come out 2nd quarter, and that the PowerBooks just got a speed bump, I think that the next iBook update will be a major one preparing for Tiger. After that, then I think it will become like the PowerBooks where they don't see an update long after average life cycle, and then release the iBook dual G4s or a G5, for MacWorld SF 2006 (or a speed bump at SF and it will be released as late as MacWorld Paris 2006).