While NCIS, which is CBS's longest-running show, is still extremely popular, it's expensive to produce. NCIS's ratings for Season 18 have been strong, but they've actually fallen since the previous season. This season averages a .85 rating and pulls in 9.65 million viewers — but that's down 24 percent in ratings and 17 percent in viewership. 

Despite the drop in viewership, CBS has confirmed that NCIS would be renewed for at least one more season. And it seems like the team is putting their best efforts in place to make sure that the plot stays strong enough to allow for even more future seasons. It'll be a huge risk to run NCIS without Mark at the helm, but the network is hoping it will pay off. It has been confirmed that Mark will be back in Season 19, but in what capacity remains unknown.