We have already heard about this in the past that Microsoft is working on an update for Windows 8/RT codenamed Blue which will bring back the Start Menu and boot to desktop option. Today, The Verge reported that their sources confirmed the same. The new Start Button will simply act as an shortcut which when clicked will display the new Start Menu. Also they confirmed the book to desktop option which will let users boot their PCs directly to old desktop screen.
Source: The Verge