Leopard = definitely something about it going to be covered, we just don't know what.
Computer updates = unlikely, except possibly the iMac, as mentioned
Display updates = also unlikely, but not out of the question
Other stuff = possible, but also unlikely
Surprise announcement = I'm thinking it'll be either a new, Macs-first graphics card, or an Apple+Sun technology partnership.
Well based on a great post of a friend in here wrlwzrd98, i think he is right on this one, and from the looks of it, its gonna be a crappy a WWDC this year for the Macintosh. But will be a great one for OSX. Well not 100% great, cause we only get a preview/beta version of the "future" (Leopard). Damn it and i was really waiting for great rumoring for this years WWDC.... damn damn damn + ive been waiting so long for new serious MacPro announcements. My situation is not undercontrol but my shrink sais its ok!
Of course on the other hand, there are a few times when all rumors came true, this time no rumors around so i cant say that a saying doesnt cross my mind, which saying? "no news is good news!"
Still living with the hope!