Windows Phone fans have more to look forward to this April than just the formal unveiling of Windows Phone 8.1 -- Nokia has sent out invitations for an April 2nd event in San Francisco that should deliver "more Lumia." The notice doesn't give any real hints as to what will be at the presentation. However, the event takes place on the first day of Microsoft's Build developer conference. Don't be shocked if Nokia unveils devices that need Windows Phone 8.1 to run, such as the rumored Lumia 630 (Moneypenny) and Lumia 930 (Martini). No matter what shows up, we'll be there to give you the full scoop.