According to the information on Microsoft’s website, Windows 8.1 is part of the lifecycle of Windows 8: Microsoft will support the Windows 8 family until January 2023, however users will be obliged to upgrade to Windows 8.1 within the next two years. Windows 8.1 was published on October 18th, and the countdown started on that day.
With this two-year limitation Microsoft is forcing users to upgrade, including the ones who wouldn’t be happy to do so. As of October 2015, users will stop receiving critical updates, new functions and improvements, and will probably be left out of apps developed by third parties. The only option for remaining safe and up-to-date is to upgrade to the latest version of the operating system.
In the meantime, Microsoft is heavily campaigning to make users stop using Windows XP and Office 2003, as still lots of individuals and businesses are using these obsolete systems. Microsoft will stop supporting these in 2014.