Vulture and Firebat icons are in there, and there are broken iconfiles for practically all of the other SC1 units.
Potentially, they just haven't gotten around to adding these units in yet, and all they have at this point is the filepaths. Alternatively, they were only planned to be added very early in development and everything was removed except for the broken icon files.
They might add more SC1 units for each race as they release the other expansion packs with additional campaigns, dunno.
EDIT: Also, the portraits for the Goliath and the Vulture can be unlocked via achievements. I think thats a pretty strong hint both units are in the game (or at least will be available in the editor). Also, theres a screenshot I saw with some heavily armored red-tinted troops armed with flamethrowers. Pretty sure those were firebats.
Blizz also confirmed that things like the Terratron/Tauren Marine would be in the editor, but obviously they aren't in it currently. :\