CBS has confirmed the renewal of all three NCIS series and all of its lead actors are also expected to return next season. The original NCIS will be on its Season 18, while the spinoffs NCIS: Los Angeles will be filming its 12th season and NCIS: New Orleans on its seventh.

Apparently, the contracts of all the leads in the three series, as well as other cast members, were simultaneously expired at the end of the 2019-20 season. That includes Mark Harmon, who served as actor and executive producer of NCIS and NCIS: NOLA, NCIS: LA lead actor LL Cool J and Chris O'Donnell, and NCIS: NOLA star and EP Scott Bakula.

According to Deadline, Harmon closed a new deal with CBS TV Studios, same as Bakula. LL Cool J and O'Donnell's contracts, on the other hand, are being finalized but both actors are expected to return next season. 

Once the contracts of all lead stars have been finalized, CBS TV Studios will discuss new deals with other cast members whose contracts are about to expire. This includes the cast members of NCIS: NOLA who are about to close their original six-year deal. 

The current seasons of all three NCIS series were cut short due to the coronavirus pandemic. It is unclear when the new season will begin production as filming studios are still in the planning stages on how to restart production amid the pandemic.

It is worthy to note that the production for returning series typically resumes after the Fourth of July holiday. But due to the pandemic, there is no clear timeline for the cast and crew on when they can return to their set locations. 

The typical September fall season launch of many TV series will also be affected if the shutdown is still in effect after July 4. The Hollywood Reporter noted the observation of many that the premiere date for scripted series could be more likely to happen in January 2021.

This means, NCIS fans will have to wait a little longer for their favorite characters to return. Moreover, the highly-anticipated 400th episode of NCIS may come much later also. 

The new milestone for the franchise had already been delayed due to the health crisis. It was supposed to be Episode 22 of Season 17. But the NCIS production has been forced to stop production in March due to the coronavirus. The recent season of NCIS was four episodes short of its regular 24.

The 400th episode will instead air in Season 18. According to EP Frank Cardea, the special episode is about how Agent Leroy Jethro Gibbs (Harmon) and Ducky (David McCallum) met.