From Google Developers:
You heard it here first. We recently received an unexpected opportunity to extend Google I/O 2012 to three days, so update your calendars. The conference will now take place from June 27-29, 2012 at Moscone Center West in San Francisco. Visit http://googlecode.blogspot.com at 9am for additional details and let us know what you’d like to see on Day 3 of #io12 at http://goo.gl/JI1jO.