The answer is maybe. Rocky Carroll, who has played NCIS Director Leon Vance since Season 5, hinted in a January 2023 interview with TV Insider that Mark Harmon could return. “I think as long as this show stays on the air, there will always be a little bit of a tease that we might see Gibbs again. Gibbs is the moral compass that we all wish we had,” Carroll said.
Harmon also hinted in a featurette for the NCIS Season 19 DVD that Gibbs was written out in a way that allows for his return. “I am not retired… As far as I know, the character lives in Alaska.” Steven D. Binder, NCIS’ executive producer and showrunner, echoed this sentiment in an October 2021 statement to Entertainment Tonight. “As an executive producer and dear friend, Mark remains an integral part of the show’s fabric… Never count Leroy Jethro Gibbs out,” he remarked.
NCIS’ executive producer Chase Floyd Johnson also confirmed in the featurette that Harmon approved of how Gibbs was written out, hinting at his return. “A very odd place to see Gibbs go, but Mark embraced it, the writers embraced it, and I think we handled it very well,” Johnson said. “He didn’t say, ‘I’ll never come back.’ There was sort of the hope that if there’s ever a need, you might see Gibbs again.”
In summary, while there are no concrete plans, there is a possibility that Mark Harmon could return to NCIS in the future.