Looks like we now have a updated version of ADMT with support for Windows 2012 R2, the version number has not changed.
At the same time there is a new version of the Password Export Server.
At this point in time I have only been able to find the updated version on Microsoft Connect.
Jump to the address https://connect.microsoft.com/directory/non-feedback sign with Microsoft and join Program Windows Server Active Directory Migration Tool (ADMT) found as shown here under Product
Azure Active Directory Customer Connection:
Download links when connected:
The documentation has also been updated:
This guide assists Active Directory administrators in performing domain migration through the use of the Active Directory Migration Tool version 3.2 (ADMT v3.2). ADMT v3.2 has recently been updated and re-released. The version remains v3.2 because it’s functionally the same as its predecessor (that is, there are no new features). This final release includes various bug fixes and can be used with all supported Windows operating systems and versions of Windows Server Active Directory.