If you are migrating to Windows 8 (RTM build 9200) and want to migrate data using the latest version of USMT for Windows 8 RTM then you should use the latest version of the Windows ADK available here. If you are unsure about the version of ADK that you have you can check the details tab of the ADKSetup.exe file. Below is the new version of ADKsetup for Windows 8 RTM (adksetup version 8.59.25584).
The old ADKsetup it listed as version 8.59.8400.
and the previous version of Scanstate.exe (from the Adksetup released to support Windows 8 RP build 8400) is Version 6.2.8400.0.
If you plan on migrating any data to Windows 8 RTM make sure you are using the latest ADK and associated files. If you have the older version installed, uninstall it prior to installing the new ADK.