I was reading a thread on here where posters were basically under the assumption that TNG can't be remastered to HD because it was shot on tape. Now, this thread went on for 11+ pages so I am not sure if this was ever corrected. But in case it wasn't or at least to reitterate the truth? Star Trek: The Next Generation was shot entirely on 35mm film, including all of its visual effects! It was simply transfered to tape for editing and compositing. So though labourous, the could re-edit the episodes together using the original 35mm masters (and using timestamps for reference).
No one ever claimed TNG was "shot" on tape. We all know it was recorded to film. It was, however, edited
to tape and the visual effects were done on tape as well (IIRC). To put the episodes in HD they'd have to be completely re-edited from the original film. While "possible" it'd like be prohibitively laborous and expensive.