That's where the "BFA DK" allied race will plant it's banner.
Haven't you noticed how they reffered to them as "allied race"?
The unlock scenario will probably involve us going to ICC to save the lich king, upon which he decides to bolster our forces with new DKs.
These new DKs will get the new scenario that was datamined; and probably start at level 50 (post-level-crunch)...