The goal is to do everything, but first and formost is to make Morroblivion playable. We have not set out specifically to do or not do anything with Solsteim or Mournhold. There is no ETA on when we might get to this. We're not even finished making Morroblivion a playable experience yet...
Solsthiem is outside of my jurisdictional boundaries. In my work on the Morrowind-ob.esm Project, my part is to fix the things people see when playing the Morrowind main quest. If someone is wanting to do Solsthiem, I would be happy to cooperate with them and share resources and information that are useful for their part of the project.