Why is that? Easy... because in Zul'gurub you never conclude it such as killing Mandokir or Jindo the hexxer. Nor do you save your baby raptor ohgan'ahnka.
And blizzard did say they may implement ZG as a dungeon or raid again.
Considering Jindo wishes to
A: keep mandokir in ZG
B: revive the remaining priests
C:Rule the world
D: hakkar is likely the child or avatar of an old god
it is highly probable we will see zg again but with different bosses and mechanics.