I actually have hypothesized, that Bethesda writers gave the OK for Morrowind to be destroyed as a nice middle finger to everybody who still like morrowind better than their new games. I can just imagine them doing the thwirly mustache thing and laughing maniacally.
Anywho, as was mentioned a couple of posts ago, the Neravarine was always a sign for change in the land and times of Morrowind, so a potential return to that character could actually be really interesting if done well (coughgetObsidiantowritethecharacters/storycough). There would be lots issues for the neravarine to resolve, not to mention gain once again the thrust of the dunmer, who've most probably forgotten of the Neravarine's existance, since 200+ years have passed since he left the shores of morrowind. Though I'm not sure about the longetivity of the average dunmer, I don't think they live 200+ years.
After having to prove him self once more, the neravarine should set out to re-enstablish the great houses or name his own new houses or something like that. Change needs to deffinitely happen. Unite the scattered dunmer, drive the Argonians/Thalmor/whoever out of the homeland and start rebuilding what can be rebuilt.
Dunmer can live up to 500+ years, so a great deal of them would still be alive. Add to that, that the people in a position of power could very possibly have survived. Ashlanders could still be alive. Everybody that supported the Tribunal temple would know who the Nerevarine was... Perhaps not personally but would have heard the stories at the very least. The artifacts that the Nerevarine had, like the moon-and-star the weapons from the Ashlanders and the items of the Hortator from the Great Houses would also prove a lot to everybody in a position of power doubting him/her.
For the rest of the Dunmer, well I'm sure they would know enough about of their own history, to have at the very least have heard about somebody that ended the blight, caused the death of the Tribunal (directly or indirectly), destroyed Dagoth Ur and restored ancestor/Daedric worship. With the state Morrowind is in, it would also be very likely that such a character would become a rallying cry faster then you can say "cliffracer"...
also from a game mechanic purpose it would be borin, because you'd already be in a position of power or at least be entitled to that position and you would already be very good in most skills and have some really high attributes, also and this is important you' would probably have to start out with some crazy ass weapons and armor. At the very least you would have Wraithguard and Sunder, the moon-and-start and I still think Keening as well, then you'd have Trueflame which is one kick ass flaming sword and a very lucky Septim...
As much as I would love it, it just doesn't sound like a very challanging game in terms of combat...