Maighstir: If visiting the past Morrowind (area) (from Skyrim's (game) perspective) is viable, why not visit the future Skyrim (area) (from Morrowind's (game) perspective)?
Skyrim's Solstheim is not in the past.
In the [url=http://www.uesp.net/wiki/Lore:Third_Era]third era[/url] (3E) in the year 427 all you went through in Morrowind happens - the blight curse, Dagoth-Ur, Nerevarine, Bloodmoon...
In 3E year 433 (6 years later) is the setting of Oblivion with the Oblivion gates, Knights of the Nine, Shivering Isle.
The ending of Oblivion is also the ending of the thrid era and therefor the start of the [url=http://www.uesp.net/wiki/Lore:Fourth_Era]fourth era (4E year 0)[/url].
In 4E year 5, the Red Mountain erupts, devastating Vvardenfell and destroying the city of Vivec.
In 4E year 16, the High King of Skyrim gives Solstheim to the surviving Dunmer, who fled Vvardenfell.
What follows are several events which ultimately lead to the situation in Skyrim, like the downfall of the Empire, the raise of the Thalmor, the great collapse of Winterhold, the great war ending with the White-Gold Concordat...
The events in Skyrim as you can play it, only starts in 4E year 201 with Ulfric killing Torygg in Solitude.
Thats 200 years after Morrowind / Oblivion.
Elmofongo: All right than how about Cyrodiil mod for Morrowind?
More likely possible since it was only 6 years apart. Still don't really see the benefit from it.
You'd either expand Morrowind with all that happens in Oblivion (including the gates) or again, have a big additional landmass with nothing to do. There's also a lot of potental conflicts trying to expand just the guilds from one game into the other - Oblivion's Dark Brotherhood / Morrowind's Morag Tong, Morrowind's Tribunal Temple / Imperial Cult in Oblivion...