The iBook recently went to 5-7 day shipping for stock units at the Canada Apple Store and 7-10 days shipping for CTO units at both the Canada and US Apple Stores. The Mac mini also just went to 5-7 days shipping.
I'd expect new updates within the next couple of weeks, and perhaps as early as Tuesday.
For both the new Mac mini and new iBook, I hope to see a Core Image-compliant GPU (eg. GeForce FX 5200, possibly with 64 MB RAM) and an increase in the stock memory to 512 MB. I would also expect to see new G4 updates, utilizing faster clocked MPC7447A chips. Otherwise I don't expect major changes, besides maybe an increase in the hard drive size, especially for the low end iBook (which is currently at 30 GB). The widescreen iBook that some have predicted seems very unlikely for this update.
Think Secret states that new iBooks and Mac minis are due next week, and will include a US$699 model for the Mac mini.