I also don't think WWDC is going to see an iBook update...and other than that, if there was going to be a minor update, I would have expected it to happen with the other consumer macs(eMac and iMac), or when they started shipping with Tiger.
My guess is that the Powerbooks are standing in front of an iBook update...so unless there's a PB update, I'm not expecting one for the iBook.
Apple has been so unpredictable lately...I see less and less reason to put all my faith in the buyer's guide. Especially as the iBook was listed as "don't buy" well before some of the recently updated Macs.
I think Apple might squeek out all they can of the current config until fall, when a G5 PB is introduced, and/or widescreen options.
I've been waiting since Feb. for this phantom update, and I will be buying an iBook soon regardless of what the buyer's guide says.