I am not claiming about Duardin unification.
A lot of people is speaking about splitting factions (Orruk or Ogors), maintain all the content (Dispossesed, Bonesplitterz, Spiderfang, BoC) and add new content always as new factions (Malerion outside Dok, Chaos Duardin, Silent People). All these is impossible without removing other stuff when in 40k to add new content they are doing all the things that they don't want for a smaller game as AoS is.