The early stuff was not not edited on SD video, or the composite effects done that way?

That would be a very dire case indeed. Like Star Trek the Next Generation where the raw footage exists on supposedly pristine 35mm, but the effects and final edits were conformed on video.

CBS is currently looking for a technological way to restore the current video masters for blu ray as transferring the film and doing it all from scratch are cost prohibitive they would also have to redo all the effects in HD cgi.