ibook pricing will stay the same. if they want something in the low price market, they will introduce a new line. I also think that they will have something for people who need more power than the ibooks but less than powerbooks (MBPs). That also might be a sub-compact. but i'm not sure. its not like a work for apple.
999 seems like a sweet spot that Apple hopes to keep. Personally I feel like laptops under 999 sacrifice worthy processors, innards, monitors(i.e. Inspirions)