I'm pretty sure Justin Sevakis made a similar post in the past mentioning the music situation, and in that very post mentioned the difficulties often involved in older dubs often not reverting back to the Japanese rights holders. It actually wouldn't make sense for an original score to revert back to the Japanese rights holder if it was an original work.
Why
wouldn't the music revert if every other asset, including performances did?
Even if the company licensing Sailor Moon couldn't initially get the rights to the old anime music (which is likely why it was re-scored), all materials associated with the dub go back to the licensor.
Any work done for the dub would essentially be a work for hire.
No, it really doesn't make sense, but thanks to Japanese copyright law, it seems all rights to anything officially-released for Sailor Moon end up going back to PNP, not even Toei. Toei doesn't even have complete control over the anime it made.
If there were an issue with the old dub music, then the old music wouldn't have been used when the license changed hands, but that the music was moved in the movies suggests that it could be used in a dub licensed to another company.
It still boils down to the question of is there ENOUGH of a market to justify the costs of producing / marketing a release. Viz doesn't get out of bed for anything less than 10,000 copies. Would they really sell that many?
They would have sold that amount had they released the old dub without making a new one, no question. Between the people who wanted to relive their childhood and, more importantly, the people who would have supported Sailor Moon in hopes of getting a new dub, they'd have hit that figure.
However, they won't sell that amount now because they actively chased away and antagonized old dub fans by investing in a new dub. The assumed that the diehard fans would make up the difference, even if it meant incurring more costs. I have a feeling they miscalculated. Because of their actions, those who would have been interested were pushed away.