Microsoft_today sent out press invites to a private event for its Surface tablet line on May 20th in New York City. The text of the invite says "Join us for a small gathering," hinting at_the announcement_of the rumored_Surface Mini device. Microsoft is said_to have been working on a smaller-screened Surface_for some time now in preparation for release_this Spring. The tablet is expected to run on the ARM/Windows RT architecture and feature a screen that's between 7 to 8 inches. In addition to its Surface event, Microsoft is gearing up to release Windows Phone 8.1 later this month.