Probably one of their abandoned hiatuses. I'd really like to stop stumbling across this author's stuff though, since he leaves so many of them in this state instead of just finishing things. Even if it ends badly I'd prefer a clean break, y'know? If he's working with an editor somewhere, they might want to sit him down sometime and ask him to stay on task with one or two series at a time. Just keep new ideas in a note for later.