Well, even if she doesn't return anymore, there are chances that she will do live performances once a while. For example, Sam Hui, a retired Hong Kong artist, still flying around Asia doing live performances once a while. So, look at the bright side ;D, maybe we have a chance to see her performing live and perhaps maybe some of the old songs she haven't performed before like Eternally, Arashi no Megami, etc.
After all, it is her old songs that've been a big hit to us right? :D( which also made me swinging back to her channel after years of not listening to her songs)