My guess is that his housekeeper saved Rush's life and at the same time pretty well blew any possible prosecution of Rush by illegally taping him and by selling her story to the National Enquirer while the investigation was still going on. His high-octane defense attorney surely knows how to make hay of that.
Rush probably does face some legal proceedings but I would be surprised if they throw the book at him.
In a twisted way, that's probably true -- better exposed then decomposed. However, I wish that someone would ask more questions about Wilma and David Cline's motives.