I doubt we will have time for filler raids this expansion. I could have seen them doing Thros/Drust aswell as AU Shattrath or Naxxramas 3.0 as first Tier after Castle Nathria similiar to Nazjatar/Mechagon, but it makes no sense to do that now that we are already attacking the Maw with the next patch. I guess we will see them again once we visit the planes of life and light in their own expansions.