Microsoft is sending invites to press for Windows Phone 8 event in San Francisco on October 29th. The event was previously a rumor, but Microsoft is making it official now by promising some additional details for Windows Phone 8 on the day, and both HTC and Nokia plan to introduce Windows Phone 8 devices in November first week, but Microsoft’s event appears to be the official unveiling for availability and could mark the beginning of pre-orders for handsets in the US.