"Starting with Vista, and continuing with Windows 7, the menubar is going away. To be replaced with things like the Windows Explorer contextual strip, or the Office Ribbon(now in Paint and Wordpad too). Many apps still retain the menubar as an option to be pinned or to be shown briefly by holding the Alt key...Firefox isn't the type of application that necessarily has contextual actions in the same way Windows Explorer does. So how to handle the functionality of the menubar if it is hidden?"
They are just using the ribbon as an example of an interface that has eliminated the menu bar. If you read further they have mockups of the 3.7 and 4.0 interface, it looks absolutely nothing like the ribbon.