The Apple Worldwide Developers Conference is taking place in San Francisco starting June 2, Monday. It's going to last five days through June 6 and Apple says 1000 of its engineers and 5000 developers are going to attend.
This year, Apple has decided to sell the conference tickets a bit differently. Instead of making all of them available at once, Apple is going to randomly pick its developer attendees who've registered for the conference.
Presumably, Apple is going to reveal the latest developments and feature in iOS and OS X. It's also possible to see more than a CPU and GPU refresh for the Macbook Air.