Microsoft on Thursday send out a media invitation to a super-secret event in Los Angeles: "This will be a major Microsoft announcement -- you will not want to miss it." Microsoft gave no hints about what it was planning to announce at the Monday event, but the best guesses so far focus on Windows 8 RT tablets and/or Windows Phone 8 announcements.

The first scenario sees Microsoft demonstrating tablets that run Windows RT, the company's version of Windows 8 for ARM-based processors.

Someone may also connect this event with Microsoft's Xbox Music service. Microsoft announced Xbox Music at its E3 press conference last week, but didn't get into specifics.

Microsoft's second event will be held on Wednesday, June 20. This one is a Windows Phone Summit, where it will provide a "sneak peek of the future of Windows Phone." Microsoft may use the Windows 8 codebase for the next version of Windows Phone, possibly allowing cross-platform apps.

Microsoft declined to comment.