In an unusual move, it appears Apple will be transmitting the WWDC Keynote Address on June 23rd, 2003. Reliable reports indicate that the Keynote will be shown live at U.S. Apple Stores with theatres. There have also been reports that there is a special event in Berlin (invite-only) which is offering a live feed of the same.
While there has been no definitive word on a live-webcast this year, there are indications that it will be available as a stream after the fact at the very least. (Note: Last year's WWDC Keynote was not web-cast.)
Other hints of things to come, include plans for significant Apple Store product-display changes in the week after WWDC, which has historically occurred with new product releases. Meanwhile, MacWorld.co.uk quotes Apple's Casanova who promises that people expecting "good things" at WWDC "will not be disappointed".
The only product that is definitively known to be previewed at WWDC is Panther (Mac OS X 10.3).