expectations:
new MB Pros
Mountain lion release date and demo
iOS 6 reveal, release window and demo
HOPES for: new, faster and streamlined itunes 11 that blows heads off moreso than even the maps app.
I dunno about iTunes 11, though I hope for it as well, but I'm currently of the strong suspicion that we might see a huge amount of the Mac line updated all at this event - maybe all of it at once. EVERYTHING is due for an update, and it'd be neat to see Apple transition to a biannual update model in which Mac models (maybe all of them but the Mac Pro, since new Xeon processors don't come that often) would get updated once in June and once in January.
I think we're likely, though, to see iLife and iWork updates; iWork's current iCloud integration is seriously half-assed compared to the way the iOS apps handle it, and that needs a real update. And iPhoto for iOS currently has better editing tools than iPhoto for OS X.
So yeah, my prediction would be:
-new iMac, MacBook Pro, and MacBook Air, possibly new Mac mini and Mac Pro, thanks to the new Ivy Bridge chipset and the new Xeon chips that came out in April. Retina display, IGZO and so forth.
-iOS 6 reveal, feature overview. Siri on the 'new iPad.' 3D mapping, free turn-by-turn (if it's not at WWDC, it'll be exclusive to the next iPhone model), UI overhaul, Siri out of beta and given some new features and services.
-Some new Mountain Lion features, mostly having to do with tighter integration with iOS devices running iOS 6 (i.e. mostly having to do with the next wave of iCloud). Possible Siri and/or dictation support; if it's there, it'll likely be exclusive to the new Macs getting announced at the event. Release date for Mountain Lion announced.
-iWork '12, with vastly improved iCloud integration.
-iLife '12, brought up to speed with the iOS versions of the apps where applicable.
-Major new awesome iCloud features.
I think iTunes 11 is possible (we're currently at 10.6.1, IIRC), but we *did* just get 64-bit iTunes pretty recently, remember. A full rewrite probably isn't in the cards, as nice as it'd be.