Yes. Yes. Solsteim needs to be an official expansion. I want to see how different this place is.
This
Seeing the Nords took over and destroyed Fort Frostmoth, Raven Rock demolished, Dunmer populated would be interesting. Solstheim is my favorite place and as AuthenticM mentioned, I'd also like to see how different and it changed. Solstheim does have a memorable atmosphere to me and did like how it represented the Nord culture. Maybe as a dlc/expansion pack, but also new or other areas included. Seeing as Skyrim takes place 200 years after the Oblivion crisis, surely things must have changed not only on Solstheim but the other islands/provinces as well. Even if Solstheim does not appear, I'd like to see some references through npcs discussing the island/recent events there or items. In Oblivion, two npcs worked on the Raven Rock colony and moved to the Imperial City once the money ran out.
http://www.uesp.net/wiki/Bloodmoon:Mead_Hall_Business - I did like this quest because you ordered mead and it shipped from Skyrim. Maybe a minor quest similar to this only involving Solstheim? Only the Mead Hall in present time there is functioning by someone else.