The Office 365 team blogged about the webcast calendar.
Future webcasts and webinars are listed on the top of this page. See Webcast Recordings below for links to recordings of previous webcasts. All webcasts and webcast recordings will be available in English only.
These webcasts are scheduled in advance, and are subject to change. You may want to subscribe to this page to ensure that you receive the latest information.
Read more at source: http://community.office365.com/enus/office365/w/o365webcastcalendar/default.aspx