Mango Will Be Called Windows Phone OS 7.5

"It's final at last folks, the next major update for Windows Phone, dubbed ‘Mango,' will rename the phone line Windows Phone 7.5."

Well, it looks like Microsoft feels 'Mango' is a significant enough update and therefore will officially call it Windows Phone OS 7.5.  Mango's main features are multi-tasking, IE9 and developer access to additional phone hardware such as the camera.