My pipe dream is for Bethesda to build an engine where you can dump the assets from Morrowind, Oblivion, Skyrim, Fallout 3 and Fallout NV into one huge Bethesda folder and launch and play any of them from one menu. They would have updated the assets to match the graphics of Skyrim or Fallout 4 or similar
If only.
But judging by how tight Skyrim kept its assets coded, and how difficult it is to import/export meshes (now), we'd reduce Bethesda to tears of laughter if they saw us talking about such a thing.