Actually exactly that happened Legion like it whas foretold in BoO.
Like Aisha said there, they returned to Shen Zin Su and if you have a Monk you can see them on the Wandering Island (which you can return to in Legion if you have a Monkcharacter) teaching young pandaren and female Gnom together Kung Fu.
Them returning in BFa as the embassy supervisors only showed that their factions have not given up the Alliance/Horde but they stay out of war.
I sadly have to agree. Except what I learned on the starting Island I have no idea what the Tushie or Huojin actually do. I even put them as wardens in my Garrison in WoD because I feel like they should actually do anything at all for the Horde.