idk, maybe a spicy opinion coming in, but I personally think that as soon as a fandom is formed, it will never die. Even if there is no official content anymore, as long as there are 1-2 people who keep making fan content, there is always a possibility for new people to join. Heck, even if there is no one left, all the content still exists! So even then a new community can be formed. So.. what I guess I wanna say is.. Vocaloid and Vocal Synths will never die, no matter how often people claim that it's dying. We have hundreds of thousands of Miku songs, like damn do you think those will all disappear??? Nah.
watch me learn japanese just to be able to translate his radios. man I hate that I love his voice so much