Public service announcement: as announced October last year, Windows 10 is now a recommended upgrade in Windows Update, meaning the installation will automatically start.
As announced last October, the free Windows 10 update has been promoted from an "optional" update to being a "recommended" one. This means that with the default Windows Update settings, the new operating system will be downloaded automatically, and its installer will be started.
The operating system will not actually install itself unattended; Microsoft says that users will be able to reject the upgrade or reschedule it for a time that's more convenient. The company has also described a variety of registry settings that suppress the upgrade.
Windows 10 will be the most popular Windows version of all time! Just look at all those people upgrading!