RoughlyDrafted has posted the first pictures of posters up at WWDC 2007-- the event of course doesn't start until Monday, but Apple is already starting to plaster the Moscone Center West with tasty morsels of what we might see there next week. As you can see, it looks like Leopard is not surprisingly going to take center stage-- the long banner in the pic above specifically references Time Machine (there's even a little logo just left of the star).
Unfortunately, there's no reference to any of the "secret features"-- MacOSXHints rounded up a good poll of what we might see there. Since I wasn't around to make predictions the other day, I'll drop one right now: like Gruber, I think Leopard will be beautifully resolution independent. Yeah, I know, not too far out on the limb, but I just got here, so I'm playing it safe.
Update: Commenter iwit helpfully points out a flickr page with even more shots.