Windows 10 (not 9 as earlier stated) will be released to the public mid 2015.
Major changes: Microsoft is now backpedalling and admitting that there is a strong base of standard desktop non-touch display users that still work on Windows based systems. This means that the OS will look at the type of computer system it is running on and automatically choose which screen to start up in. If you have a touch capable display, you will see the now familiar Start Screen (or Modern UI) with the touchable tiles to launch programs. If you have a standard desktop computer, Windows 10 will start up with the older (legacy) desktop screen - similar to to the older Windows XP, Vista, and 7 desktop. You will still have access to the Start Screen if you like. It has not been determined which screen you will start at if you have a touch screen capable desktop system but you will be able to change your start up screen regardless.