Sprint just sent along an invitation to a "collaboration event" on April 4th with Sprint CEO Dan Hesse and HTC President Jason Mackenzie. The purpose of the event is still a mystery, but rumors have been swirling that Sprint will receive the HTC One X (currently billed as an AT&T exclusive), so it could be an announcement for a new flagship device. Of course, nothing's been confirmed yet, but we'll be attending the event and will find out soon enough.