It is very unlikely, but I do hope they'll let us thread the ground of Morrowind once again, if only briefly.
The problem with this is that Blacklight could be made into a really interesting city, as previous posts suggest.
However that sounds so huge it could be an independent DLC, which make the inclusion of Blacklight all the more improbable...
On the other hand, how did the Corprus diseased creatures we see in the trailer get to Solstheim?
I don't remember seeing any of them on the island in Bloodmoon...
Corprus was a disease you caught, devised by Dagoth Ur, also known as the Divine Disease. You didn't change immediately. Some may have caught it and carried it to Solstheim while looking for work in Raven Rock when it was still a mining community before money dried up, as was stated in Oblivion.
As for Blacklight...I think people are getting carried away with their...Headcanon interpretations...
Even if they did put it in, it would never live up to the expectations some of us have created for ourselves.