One of my absolute favorite games on the Wii! I was interested in the game when Hitoshi Sakimoto and his crew at Basiscape composed the soundtrack, which, is otherworldly and reminds me of Phantasy Star Online in some aspects. There were rumblings from Artepiazza back in 2017 that something was happening with possibly a remaster for Switch or even a sequel, but nothing has ever been announced. Guessing because they've been busy co-developing the Dragon Quest and SaGa games of late.
Opoona reminds me a bit of EarthBound, with its charm and a game that kinda allows you to do whatever you want within reason. I would love to see it cleaned up and given some new features like escaping from battles, a playtime counter, and maybe an easier way to figure out where to go because the beginning can be very confusing on what you're supposed to do.
Overall, Opoona is a treasured gem in my collection and Artepiazza still posts sometimes talking about the game, but Koei is the publisher and unless someone else helps out (maybe Nintendo could publish), we might not see anything else as it didn't sell too well.