There's a hole in the Moscone Center schedule, and it's filling up with a 'Corporate Meeting' -- looks like it might be time to start booking those flights and hotel rooms, developers. June 5 to June 9 is blocked off on the conference center's schedule, and similar bookings have in the past turned out to be the annual WWDC slot.
AppleBitch.com, which spotted this booking, also points out that there are single-day events in May and June also allocated to 'Corporate Meeting.' These might be for Apple events and product introductions, or they might not. MacRumors notes that the presumptive WWDC 2011 dates line up nicely with the 'Moscone Stone' longterm bookings calendar that revealed the 2010 event's timing.
While the last WWDC was focused on iOS and iPad development to a very high degree, it's expected that this year's event will include much more Mac content; the expected release of Mac OS X 10.7 Lion will drive many of the conference sessions.