John Gruber reading between the lines:

On Tuesday morning, Presidio [the big, keynote room] is booked for the Developer Tools Kickoff, Game Technologies Kickoff, and What’s New in Cocoa sessions. After that, Presidio is pretty much entirely “TBA” from Tuesday afternoon through the end of the day Thursday.

This implies not just that Apple will be announcing new stuff (duh, it’s WWDC), but new stuff that will fill the biggest room in the building with two-and-a-half days worth of sessions.

Reading Into the Preliminary Schedule for WWDC 2012