I don't think my favorite author is writing off Robbie. In the chapter just posted, it is clear that Brad has not given up on him and he even pointed out to Will why it may be in his self-interest to make the first conciliatory move toward Robbie. Of course that was rebuffed, but things are never easy, so what else is new?
While the shenanigans of the younger CAP generation remain filled with adolescent angst, Robbie has in many ways often made things interesting as well as he seems to stumble through his family relationships. Who else could fill his role?