Microsoft announced that a public preview of Windows 8.1 will be made available on June 26th. The final release of Windows 8.1 will be provided to all Windows 8 and Windows RT users as a free update. There's a catch though, if you decide to test the Public Preview you will need to reinstall all your applications from scratch if you upgrade to the final release of Windows 8.1:
As with the Windows 8.1 Public Preview, the final release of Windows 8.1 will be provided to all Windows 8 and Windows RT users as a free-of-charge update appearing in a system notification. Users need simply acknowledge the notification and allow the Windows Store to upgrade the operating system. That is, unless you've been trying the public preview.
Microsoft's reward for its army of unpaid beta-testers: a migration from Windows 8.1 Release Preview to the final retail release will see users having to reinstall all applications from scratch. While personal preferences and data will be retained, any application - whether a Modern UI app installed through the Windows Store or a traditional Desktop application installed manually - will need to be reinstalled before it will operate correctly. Windows RT users are saved half that job, thanks to its lack of support for legacy applications - but will still need to reinstall all Modern UI apps.