Captain Marvel could potentially set up the upcoming Black Widow movie. The recently-released one-sheet poster for Captain Marvel gave Blacklist screenwriter Jac Schaeffer an unexpected writing credit; given Schaeffer is working on the script for the Black Widow movie, that definitely seems to imply there's some sort of connection between the two films.
Captain Marvel increasingly feels like something of a prequel film for the entire Marvel Cinematic Universe. Brie Larson has described the movie as an origin story for Nick Fury, it essentially sees Carol Danvers serve as the inspiration for the Avengers Initiative, and will even reveal the backstory of Ronan the Accuser, villain of the first Guardians of the Galaxy. The recent second trailer featured a subtle link to The Avengers with a blink-and-you'll-miss-it reference to Project P.E.G.A.S.U.S., which may potentially mean an Infinity Stone will crop up in the film too. But, while all these connections are exciting for Marvel lovers to spot, it's important to remember that Marvel will be hoping Captain Marvel will launch some new concepts and ideas too. Jac Schaeffer's writing credit suggests it could serve as a subtle springboard for the Black Widow movie.
Captain Marvel is set in 1995, and when the films kicks off, Nick Fury is a disillusioned S.H.I.E.L.D. agent who's close to quitting from the spy game altogether. It seems clear that Fury's encounter with Captain Marvel will transform his career, giving him an exciting shot of ambition that will lead him to ultimately become Director of S.H.I.E.L.D.. But here's the interesting thing; it's generally believed that Black Widow will serve as a prequel film as well, revealing how Natasha Romanoff joined S.H.I.E.L.D. in the first place. If that's the case, then Black Widow will also be set (at least partly) in the '90s as well.
According to the MCU's official timeline, in 1993 Natasha Romanoff was recruited into the Russian Red Room program. While the Red Room had previously served the Soviet Union, it looks as though the political upheaval in Russia in the early '90s led to a change of approach. The Red Room appears to have instead started selling its operatives to the highest bidder as mercenaries. Over the next few years, Natasha would be trained to become the Black Widow, one of their best; she'd gain a dangerous reputation, and in 1998 would be hunted down by S.H.I.E.L.D.'s best agents - one of whom was Hawkeye. Hawkeye saw some hint of potential within Natasha, though, and he gave her the opportunity to defect. It was one that Black Widow took, and she joined up with S.H.I.E.L.D..
If Black Widow is indeed a prequel, then at least some of the events must be set in pretty close proximity to Captain Marvel; that raises the possibility that there will be a direct connection between the two films, which would explain Schaeffer's becoming involved in both projects. The most obvious potential connection is Nick Fury himself. After all, Captain Marvel will set him on the road to becoming S.H.I.E.L.D.'s Director; perhaps Black Widow will be another step alo ng that path. It's hardly a stretch to imagine that the hunt for Black Widow didn't just involve Hawkeye; Fury could easily have been the man running that operation, with Hawkeye working as a Specialist in the field. If that's the case, then successfully recruiting one of the Red Room's most dangerous assassins would be a very nice feather in Nick Fury's cap, and potentially a major step in his career in the Black Widow movie.