Interesting find in the recent Q&A

[Blastboy]

"Transmog appearances that have rep requirements will be unlocked account-wide once earned. You won’t need to re-earn a specific reputation on an alt if you want to use their tabard as part of your outfit"

Will some prestigious tabards known to be connected to a long grind now be worthless? Will tabards out of your level range no longer be transmoggable?

 

[Dcm]

This topic was brought up somewhere around the forums some time ago, however you do bring up interesting points. I was under the impression that it was only applying to items such as Shado-Pan helmet, Laughing Skull Mask, etc.

As far as tabards and level range, I feel as though this was always something in the game. Meaning, any level can obtain reps from Draenor (via legion medallions), or Mag'har, Baradin's Warden's, etc etc, so that's why these mogs were available to us if we were to obtain the needed reputation. However, tabards such as Dueler's Tabard (it is obtainable by us, but it was not intended) cannot be mogged by us.

So to answer your question, I believe that yes potentially the more prestigious tabards are going to be null and void, but anything with or without a gated level requirement will remain the same way.