While I can understand a Blu-ray release of the Muppet Show to some degree given its PAL provenance and somewhat higher resolution (576i), 4K would be utterly pointless. Unlike other British TV shows of the same era which had exteriors shot on film, The Muppet Show had no exterior photography.
At this stage, the only way I see Fantasia being worth a rerelease on disc is if it’s released with an uncensored roadshow version, which screams some sort of limited edition boutique release.