At this point, both Daniel and Jeph have told all of the stories on their respective titles that they could, although it’s not out of the question that one or both of them could return in the future. As far as other books go, life is change–so while, at the moment, it doesn’t seem like any other writers are going to be vacating their present assignments, that could all change tomorrow if something happens somewhere (and not necessarily something bad–a new assignment could open up, or a new opportunity could arise for somebody.)