That's a neat question.
I imagine there'd be stuff akin to Casablanca, with cloak and dagger and stuff in the shadows, but the "star" is dragged through the muck of it all without a chance to surface and breathe until after the fact, or something like that.
There was also the Le Carré stream of espionage fiction that would have chugged along which owed nothing to Fleming. More literary and realistic but also very popular and often made into films. "The Spy Who Came in from the Cold", "Tinker, Tailor, Soldier, Spy", etc.
Without Ian Flemming, Roald Dahl would probably have found another way to make a few bob post war.
They were both intelligence officers during the war after all.
The spy genre pre-dated Ian Fleming, and pre-dated established spy agencies. The movie, Goldfinger established the Bond legacy. Had the series ended with Dr. No and From Russia with Love, we wouldn't be talking about it now. I'm currently wading through Daniel Silva's Gabriel Allon series, and wondering why there never was a KGB super-spy novel series. I asked my librarian to look up Donald Hamilton who wrote 3 decades of Matt Helm novels, but they never heard of him. Fickle world.