Skyfall director Sam Mendes will get the cameras rolling on the next James Bond movie (which is currently without an official title) by the end of the year, in order to have the film ready for a Fall 2015 release. Part of the reason that production hasn't already begun is because it took longer than anticipated for Mendes to commit to directing; he was concerned about being able to properly manage the project, given his other commitments over the past year.
The other reason that James Bond 24 didn't start principle photography this past month (as was once the plan) is because the script required some tinkering beyond what was expected, to get it in shape and ready for shooting. Most recently, it turns out another screenwriter was brought in to assist with that task.
The New Yorker (hat tip to /Film) did a piece on screenwriter/playwright Jez Butterworth, where it came to light that he had done some polishing on the Bond 24 script draft, in consultation with Mendes as well as current James Bond actor, Daniel Craig. Butterworth also did uncredited work on the Skyfall screenplay, it turns out, so it's possible he shall also go uncredited for his contributions to Bond 24 - contributions that he summarized as follows:
“You know, like Bond doesn’t have scenes with other men. Bond shoots other men—he doesn’t sit around chatting to them. So you put a line through that.”
Bond 24's first script draft was penned by John Logan, before it was reportedly revised by Neal Purvis and Robert Wade (who injected more wit and humor into the mix); all three of the aforementioned scribes also collaborated on the Skyfall screenplay. That is to say, between their involvement and the assistance provided by Butterworth - who, in collaboration with his brother John-Henry, cowrote the sci-fi thriller Edge of Tomorrow and James Brown biopic Get on Up (both were overall well-received) that released earlier this year - Bond 24 should match or exceed Skyfall, in terms of script work quality, while building on that film's story.
Mendes will also have newfound experience gained from his time making Skyfall, to draw from and help ensure that Bond 24 surpasses its predecessor when it comes to the film's spectacle. Skyfall was an especially lucrative Bond installment (it grossed more than $1 billion worldwide) and received positive reviews by and large, though it arguably fell a bit short when it came to staging action sequences. And Bond 24 won't have Roger Deakins' cinematography to help make up the difference, unlike Skyfall.
Craig will be joined in Bond 24 by his Skyfall costars Naomie Harris, Ben Whishaw, and Ralph Fiennes. The list of newcomers will reportedly include Léa Seydoux (Blue is the Warmest Color) as a "femme fatale" of sort, as well as Guardians of the Galaxy's Dave Bautista, as the latest in a long line of dangerous Bond villain henchmen.
James Bond 24 opens in U.K. theaters on October 23rd, 2015, followed by its U.S. premiere two weeks later on November 6th.