Come on guys, it is a graduation. We've always wished Coco or Aqua would show up again someday, but that is not a certainty.
Now Ame is the first in Holo that graduates, but seems like she have a contract that allows the IP alive and she can be involved in a very huge collaboration, think of surprise appearance during the next HoloEN concert, a Myth girl starts singing Chiku Taku, then suddenly Ame shows up.
It is interesting, since Cover really needs to hold on their lucrative IPs, they have to explore this avenue of graduation. Letting IP just go into the abyss hurts, now there's another way.