Re: Morrowind
I'm not too interested in the Morroblivion or Skywind projects. I'm more interested in OpenMW. An open source implementation of Morrowind has the greatest potential to open up the game's moddability. Of course, this all depends on how extensively the code continues to get developed (beyond the initial goal of simply recreating the vanilla game).
The original game is already quite moddable, but lots of mods are pretty clunky or difficult to install, and there are definite limitations to what mods are currently able to do. If the underlying game code were designed to support what these mods are trying to do, everything would work better.
Long term, it's easy to imagine that OpenMW could add optional physics, better support for NPC schedules, better support for updated graphics, and many more scripting functions that don't currently exist in the game. Whatever features have sufficient interest could potentially end up in the code, while always maintaining support for the original features of Morrowind.
Trying to put the Morrowind world into Oblivion or Skyrim would just introduce a new set of limitations and compromises. I think OpenMW has the most potential to let players turn their Morrowind game into whatever they want it to be. It's a huge project though so who knows if it will ever really reach this potential. At this point they're just focused on getting it to run the original game correctly.