Microsoft has sent out a cryptic invitation to select reporters for an upcoming event being held on Monday, April 12th in San Francisco. The notice itself doesn't mention much more than that the tag line "it's time to share," but already speculation is running rampant as to what exactly Microsoft has in store.

Some say Microsoft's Courier may be shown off in an effort to steal some of Apple's tablet thunder. Another perhaps more plausible theory is the introduction a Microsoft-designed consumer phone ahead of the debut of their new mobile phone platform later this year. Previous leaks have had two Project Pink phones, the Pure and the Turtle, shipping April 20th for Verizon – which would line up nicely with an introduction the week before.

The phones are rumored to be labeled as "Sharp+Microsoft," have touch screens and slide-out QWERTY keyboards but none of that is official. Whatever they plan on announcing next week, chances are it has something to do with the mobile front – feel free to speculate in the comments section. Meanwhile, Apple has its own event planned for this Thursday, where it is expected to introduce the next version of the iPhone OS.