The episode description only says that Director Vance will be notified that a nuclear submarine carrying Gibbs and Bishop has gone radio silent, with no details of what’s in store for Ducky.
Will it be the hour of Ducky’s goodbyes?
Or just another case?
Now, as much as Ducky walking out on that note and with a “Goodnight” sounds like the character making his grand exit, he does have at least one more appearance in Season 16, as he appears in promo photos for the March 26 episode, called “Silent Service.”