Solstheim? Meh. I'd rather have them focus on Skyrim only.

I'd like to go back, see how it's changed. See if the imperial fort is still standing or if it has succumbed to nature or been overthrown.

I've read a bit into Infernal City, but I can't recall if I got to the part referring to the fate of MW or not (though I've heard enough about it anyway). Since Skyrim is set to take place shortly after Oblivion, I have no idea whether or not the Argonian invasion would taken place yet or not, unless Infernal City mentioned the events as taking place either during or shortly after Oblivion I'd have my doubts. I also recall there being rumors in Oblivion about the Nords wanting to keep Solstheim for themselves as well, although that doesn't appear to be how it ends up working out obviously.

As for whether or not I'd like to see it-it would be okay as long as they include a lot of changes-like new settlements, expanded versions of the settlements seen in Bloodmoon, and a number of new dungeons (perhaps some were buried in the snow before and have become uncovered). Overall it would need to be familiar enough to satisfy fans of the Bloodmoon expansion yet with enough changes to make it more than a carbon copy of a place that we've already been to.

Ultimately however I think it would be better handled as a community-created mod-Bethesda should be dedicating their efforts to the mainland anyway. Doing Solstheim as an expansion would be unwise as well for the simple fact that Solstheim is too much like Skyrim-there wouldn't be much at all to provide in terms of new content, plus it would feel even more like a rehash of Bloodmoon.

To sum it up-if they include Solstheim as part of Skyrim-no big deal, if they don't well there's a nice idea for a mod, but if they add it with an expansion it'll be pretty lame-especially if modders are already working on recreating it themselves by that point. lol