It seems to me that a lot (if not all) of the rich Dunmer culture appears to have been lost. In Morrowind, you were given this very alien world filled with these (mostly xenophobic) people that were staddling tribalism (the old, struggling Ashlander tribes) and traditional feudalism (seen in the various major Houses). They seemed to be very resistant to Imperial assimilation, to the point that they demanded certain allowances in their agreement/charter for entry into the Empire -- for example, slavery is still legal (to my knowledge) in the province of Morrowind, they have peculiar religious practices (as far as I know, they lead the way for Daedra worship), legalized/regulated assassination, and other such things. They even have some unique slang terms.
When Oblivion came out, the game had some references to these cultural things but most of the NPCs had an Imperialized attitude of, "Well, those people were savages. I'm a proper civilized citizen." Okay, I guess I can see that, but it surprised me that there weren't any real noteable merchants or other travellers who were strong in the old ways.
Between that time and Skyrim, there was the Red Year, and a mass exodus from Vvardenfell. To my knowledge, most of the Houses appear to have collpased (have any survived at all?). So, in Skyrim, all of the NPCs just appear to be regular Cyrodillic citizens who just happen to be prejudiced against by the Nords. They've got none of the fire or intrigue you saw from Dunmer in the Morrowind game.
So, do you think the Dunmer culture has been lost for good? Are they now just Imperials in grey? Or is it a fault of the design of Skyrim's NPCs? (( This is not meant to be a shot, but I do feel that the developers have REALLY downplayed the racial tensions in the game for the sake of broad playability and trying not to offend anyone. As I mentioned in another thread, Ulfric is just as happen with his altmer minion as he is with his Nordic one.))

the religious practices are touched on a bit though. i'd say the lack of reference in skyrim is just the npcs as none of the other races aside from nord (which makes sence in a way it being their province) get a lot of reference reguarding their cultures either. As i mentioned earlier though try the lore forum i think they had a discussion about this a few weeks ago 
a'int no way they can get it back or even have it be remotely the same. even the Daedra couldn't invade Black Marsh.