the dreambubbles were destroyed by the black hole and sucked outside of "canon," into the fanfic land that is candy earth c. all the surviving ghosts are there.

in regards to what sinistral says, this is a larger symptom of the "narrative sieving" that happens post-canon: one world with everything that matters (alive characters, sburb, plot) and one world with nothing that matters (ghosts, getting married, having kids). the funny thing is that act 6 was already about that, too.