I have just compared the C:\Windows\PolicyDefinitions folder on the Widows 8 preview build with a Windows 7 Enterprise build. And unless I missed one, the below ADMX/ADML files are new.
AppxPackageManager.admx dam.admx DeviceCompat.admx EAIME.admx EarlyLaunchAM.admx EdgeUI.admx ExternalBoot.admx msched.admx ProximityCommon.admx srm-fci.admx UserState.admx WindowsHistoryVault.admx WinStoreUI.admx wlansvc.admx WPN.admx WPN.Provider.admx wwansvc.admx
When you open the related ADML files stored under C:\Windows\PolicyDefinitions\en-US you will find some interesting hints about what these new policies are supposed to do. You will find stuff about Windows to Go, the App Store, Profiles and more.