MacRumors.com

One AppleInsider.com thread indicates that Low End PPC970 PowerMacs will be immediately available at WWDC... while mid and high end range machines will be delayed for approximately 5 weeks.

Meanwhile, according to the post, 15" PowerBook updates are not expected at WWDC.

Shipping low-end PowerMacs would be consistent with previous rumors from MacBidouille. If you believe their early reports, they claim 1.4GHz machines were in production in May, 2003 -- and would presumably be the "Low End" versions.

PowerBook update rumors have been ongoing for months... with vague hints (and not so vague hints) at impending updates.

Addendum: Meanwhile, MacBidouille posts an unconfirmed rumor that states just the Top End PowerMac will not ship immedately (translation by MacCoaster):

The PPC 970 Power Macs should be available as soon as their announcement at the WWDC except for the High end model which needs two more weeks. They should arrive to the distributors in the weekend.

Not much longer... :)