RygariusAdmiral Taylors Großschwert
will be eligible for transmogrification in an upcoming 6.2 PTR build. To keep things fair, there will also be a Horde equivalent (in a different color) as a treasure that could be found in the Jungles of Tanaan.
If the item has been misplaced in the time since it was originally obtained, there will be an in-game way for players to obtain the sword again.
It will likely be a vendor. Details are still TBD at this stage.