As I said earlier, the Dunmer(Chimer/Velothi) as a people are gone. Their genetic bloodline is still there, but the culture is gone. There are colonies in Soltheim and Skyrim, and you bet that the influence of the Skaal and Nords will change the Dunmer culture. The rest of them are dead or scattered through the rest of Tamriel. They are not going to return to a single Dunmer culture even if they manage to retake and resettle their land.
I was thinking about this exact thing today...
We should view what happened to Vvardenfell as the fall of a civilization, rather than simply a tramatic event. At the End of the Third Era, and the beginning of the fourth, the Vvardenfell experienced a series of catastrophes: A civil war, two invasions, and two catastrophic natural disasters. At the same time an important bedrock of a unique Dunmer culture --- that is, the Almsivi Tribunal --- was destroyed and discredited completely.
Just imagine if, say, the United States experienced a tragedy of equal magnitude (in order): Christianity is completely discredited, a vicious civil war breaks out, Russia invades, retreats, a meteor destroys NYC, Yellowstone Volcano explodes and coats the entire breadbasket of the U.S. in a foot of ash, blocking out the Sun for months on end, to be followed by an successful invasion by Mexico to reclaim its lost territories (think the entire southwest) plus some. Think the U.S. will survive that?
So, like what Lady Nerevar said, we are seeing a permanent change in what it means to be Dunmer. Many things that defined Morrowind and its inhabitants as unique have been challenged and destroyed. Slavery, gone. Tribunal worship, gone. Hundreds, if not thousands of cultural and heritage centers, destroyed. Countless native Dunmer artists, musicians, mages, potters, writers, weavers, teachers, elder wise men and women; all conveyors of Dumer culture to the new generation...dead.
I guess the important question now is how will the Dunmer change? Post Land-Fall, how will they define themselves? They will undoubtedly be heavily influenced by the Skaal and others. And while I don't agree that the Dunmer will ever be able to reunite under one culture should they reclaim Morrowind, it'll be quite different than the one the Nerevarine left in TESIII.