I wouldn't say Vocaloid is dying. It may not be as popular as it once was but Vocaloid still has a large and dedicated fandom with many active communities, as well as new fans each day and several live concerts a year that get sold out pretty quick.
I'm relatively new to Vocaloid and from what I can see, things will last for quite a long while. Regardless, I choose to enjoy the years of accumulated content and perhaps even add my own. Who knows, things may even rise back up again. As said in Sand Planet, things are in the hands of the next generation of fans.