Hello,
Windows 8 may be supported in SEP 12.1 RU2.
Incase, if you are interested in Beta Testing for SEP 12.1 RU2, check this :
https://symbeta.symantec.com/callout/?callid=1D5D3DD349C248E69B13977DA4DBF426
The Symantec Beta Program is now accepting applications to participate in the Symantec Endpoint Protection 12.1 RU2 Program which is scheduled to begin in early July.
In order to be considered for this program you must be registered with Symbeta. If you are already registered, log in with your username and password. If you have not yet registered, you will need to create a Symbeta account and provide the necessary information.
Hope that helps!!