It was hinted that the show's future was uncertain so the producers decided not to end the show with a cliffhanger. Instead we were left with what would have been a good way to close the show. Mac solved his last unsolved case, which i find odd; when the show began Mac said that at one time he had 10 unsolved cases and that the number tripled even quadrupled, so we are to think that during these past 7 seasons Mac solved all of them, offscreen. I wonder why they never had an episode of him solving one of those cases. But I guess because of the uncertain future of the show, the producers felt it was best to end it that way. And also Mac was uncertain of his own future. And Danny made sergeant at the end. So when the show comes back, does that mean Danny will be Mac's superior? Or will Mac no longer be with the crime lab?