Patch 9.2 Build 41257 is currently being deployed, and this build brings a new Jailer model! This model matches the armor he's seen wearing at the Sanctum of Domination Finale Cinematic and presumably the model we'll see on his fight at the Sepulcher of the First Ones.
Here is the model side by side with the Jailer's model from previous patches.
Patch 9.2 PTR Build 41257 DataminingChoose Between Succubus or Incubus Models 9.2 PTR Development Notes Class & Tier Set ChangesTier Set Changes Models. Read more on wowhead.com