Short Answer: Spin-off with side characters... or ones who are only implied
The latest Bond movie, No Time to Die, is officially the 25th in the franchise, one of the largest and longest-running of them all. And the star is on record as saying he is done with being Bond.
There has been a call to re-make the character as Jane Bond, and that works if you ascribe to the fan theory that there is no "James Bond" as such, that this is just the code name for whatever agent current holds the 007 designation. (Which makes much more sense to be than the theory that has Bond as Dr. Who-like time lord). Many such a character name turns out to be job title, such as Green Lantern and (spoilers for Princess Bride) Dread Pirate Roberts.
There have been pretenders to the Bond throne too, from Jason Bourne to the new Kingsman series.
So maybe it's time to give Bond himself a break and explore his larger world. Some possibilities:
What if 007 graduates, potentially, to becoming M? While both Connery and Moore are, sadly, gone, Pierce Brosnan would make a great M. Wouldn't it be interesting to see what M does all day? All the various agents and cases that administrator oversees? All the other governmental departments, and foreign counterparts, they interact with? There may not be as much action down that road, but intrigue can still be intriguing.
Another path to consider is that of Q's. Yes, gadget-inventing is interesting, but I'm talking about having Q leave the lab for... reasons. "But I'm not a field agent!" he protests. "You are today," M tells him. I see this as a sort of high-tech MacGyver adventure. Q lacks Bond's combat skills, but he is smarter and more disciplined. He could find a clever way to thwart a threat that Bond would never come up with. Ben Whishaw, the current Q, easily has the charisma to star in a movie. Also, since he is not 00 designated, he cannot kill and so is forced into even cleverer solutions.
Are these too stuffy and geeky, respectively? Well, there is another agent we could follow: Felix Leiter. At least seven people have played this role, meaning that it's another code name/designation... or that Mr. Leiter is a master of disguise. (Spoilers for No Time to Die) Yes, he dies in the new movie, but when has that ever meant anything in movie-dom? For all we know, there are as many Felix Leiters as there are Black Widows, which could also explain the variety of his appearance. Or we could show Felix's origins, or even revisit the Craig films from his standpoint, Rosencrantz-style.
And if all of these leave you cold, we learn in Thunderball that there are nine agents with "00"-- or license-to-kill, um, licenses-- from 001 through 009. Fleming himself mentions 0011in the Moonraker novel. So... what are all of these other agents busy with? Yes, some we know, but we also know that-- if both the novels and the films are canonical-- that several of the numbers have been recycled; there have been at least three 003s, one of whom was a woman. What are the other 00's adventures like?
Also, we have had white guys as M and then a woman-- Dame Judy Dench. So this time, we have to switch it up again, demographically speaking. Alexander Sidding, some will recognize from A short stint on Game of Thrones, but more as Dr. Bashir on Deep Space Nine, is my vote. There is sort of an in-joke here. While Capt. Picard role-played on the Holodeck as a film noir detective, Dr. Bashir role played there (or "there"?) as a Bond-esque agent. The joke-- he's now IN a Bond movie... and is still not playing Bond.
The future of the Bond series may in fact lay... beyond Bond.