It is a confirmation. Windows RT devices – the edition of Windows 8.x for devices with ARM architecture like some tablets – will not benefit from Windows 10. However, Microsoft will indeed offer them new features.
WinBeta noticed a recent addition to Microsoft's Windows 10 FAQ. It says about Windows RT: " If you are running Windows RT, your device will not be upgraded to Windows 10 but we have an update for you around the release of Windows 10. "
However, we still don't know the new features inherited from Windows 10 that will be offered for Windows RT.