Yamaha's Twitter has been dead since December. But they've done hour-long server maintenance a few times before and absolutely nothing changed visibly for users visiting the site. Actually, the only time there was server maintenance and something significant happened after was when V5 came out, but we knew it was happening because they announced several products being discontinued a couple weeks prior. (And the maintenance was much longer than 1 hour for that case.)
Part of me wanted this to be something, but the maintenance is only an hour and I feel like at this point if there were to be a new Vocaloid, the company producing it would have let us know (if it were a new Vocaloid, it most likely would be one of the surviving/active companies, in my humble opinion).