If it was shot on tape then there is no hope of an HD remaster. However if it was shot on film then the film can be scanned by high-resolution cameras and digitized at a higher resolution than it was capable of being broadcast originally.
Steve Guy
I just looked it up and the information I've found said that it was shot on 35 mm film and has in fact already been digitally remastered, but at least as of 2019 the only place to watch the remaster was amazon prime video. I wouldn't be surprised if its been released on blu ray by now, or if not maybe they're waiting for an anniversary.