In an attempt for Microsoft to become the new Borg, next year Microsoft will be adding Windows 10 to the recommended list of updates for Windows 10. They have done this recently as a “fluke” but have since moved the goalpost until 2016.
Adding this upgrade to the recommended list will automatically download it to your system if it is capable of running Win 10. It’s a waste of space and bandwidth to do it this way, but Microsoft really wants people to flock into their Garden Of Eden Cortana.