No, I think you misunderstood me. The original guys getting too old for the job, so they hire new recruits, and spend the movie taking the recruits on some of their various missions to train them. We will still be seeing plenty of the orginal guys because, like you said, they are the Ghostbusters. At the end, there will be an enemy so powerful it takes both the old and new Ghostbusters to stop it. Ans at the end, the originals can retire.