It will be part of the MCU's phase 4 line-up.
Phase 4 starts after "Avengers 4" with "Spider-Man: Homecoming 2" (July 2019), and will also include "Guardians of the Galaxy Vol. 3," which doesn't have a release date yet.
Jac Schaeffer is writing the screenplay.
Scaheffer wrote 2009's "TiMER," the short "Olaf's Frozen Adventure," and 2019's upcoming "The Hustle," which stars Anne Hathaway and Rebel Wilson.
Johansson is reportedly contributing ideas to the screenplay. In 2016, Johansson told Variety about the endless possibilities for Black Widow film:
"There’s a lot of places you can go — you can bring it back to Russia. You could explore the Widow program. There’s all kinds of stuff that you could do with it. You could really uncover the identity of who this person is, where she comes from and where she’s part of. There are so many ways you can go. I think it would just have to be very much like its own specific thing. It would have to have its own specific vibe. It would have been totally different than any of the other standalone films. I think if the fans wanted it enough, then it would probably become a reality."
Filming will begin next year.
This probably means that the movie will come out in 2020 or 2021, depending which half of 2019 filming takes place.
There have been rumors that the movie will be a prequel featuring Bucky Barnes as the Winter Soldier.
This would likely show Natasha during her early years in the US after the fall of the Soviet Union, when she first gets involved with S.H.I.E.L.D. Since Hawkeye and Natasha work together for years before the Avengers forms, it's safe to assume that he will be in the movie as well. But then again, we also assumed he would be in "Infinity War."
Winter Soldier's involvement could be quite significant. In "Captain America: Winter Soldier," Natasha mentions a run-in with him, and it probably wasn't just throwaway dialogue:
"Five years ago I was escorting a nuclear engineer out of Iran, somebody shot at my tires near Odessa. We lost control, went straight over a cliff, I pulled us out, but the Winter Soldier was there. I was covering my engineer, so he shot him straight through me. A Soviet slug, no rifling. Bye-bye bikinis."
Anthony Mackie has expressed interest in appearing in a Black Widow movie.
Unfortunately, if the movie is a prequel, it's unlikely that Sam Wilson/Falcon would be written into it, since he didn't join the team until "Winter Soldier."
According to reports, Scarlett Johansson will make between $25 and $31 million for the movie.
Not confirmed, but this would make Scarlett Johansson the highest-paid female actor.
Marvel looked at over 65 directors to take on the project.
In late April, a report surfaced that Marvel Studios had interviewed over 65 directors for the Black Widow movie, with the intention to hire a woman. Before Marvel announced that it would hire a female director, "Thor: Ragnarok" director Taika Waititi said he'd be interested in directing a Black Widow comedy.
Cate Shortland is the frontrunner.
Shortland is an Australian director of film and television. Her first feature film, "Somersault," came out in 2004. 2012's "Lore" was submitted for a Best Foreign Film Oscar, but didn't make the cut. Her third feature, "Berlin Syndrome," based on the book of the same name, premiered at the Sundance Film Festival in 2017.