There are already applications like
https://www.topazlabs.com/topaz-video-ai and
https://tensorpix.ai/ -- So it doesn't seem unreasonable that some of these deep learning models could upscale all these old TV episodes to at least 4k.
I'd love to see a combo of this Google tech and AI upscaling do the same for Babylon 5. They had shot the actors in widescreen format, but the CGI spaceships were only rendered in 4:3 and the files have been lost.