It is said that No Time to Die will be the twenty-fifth and last Bond movie made. There are two possible reasons. First, it is likely that the Broccoli franchise was only allowed to make 25 Bond movies. Second, I think exhaustion is most likely, and not just any old exhaustion, the sexual exhaustion of five ageing actors, not to mention James Bond himself. 

At the end of the novel, You Only Live Twice, James Bond is missing presumed dead in Japan.