According to Deadline, Marvel is getting close to finding a director for its Black Widow solo movie.
The studio is narrowing down its list of female directors and Deadline reports Cate Shortland could be the choice:
Biding its time by putting her in The Avengers and other superhero titles, Marvel is moving forward with a Black Widow film with Scarlett Johansson. While they are looking at female filmmakers, Deadline hears keep an eye on Australian helmer Cate Shortland on the short list. Her recent credits include Lore and most recently Berlin Syndrome. Stay tuned.

Black Widow would be Marvel’s second solo film centering around a woman as the lead. Captain Marvel, starring Brie Larson, is the studio’s first solo female movie. Ant-Man & the Wasp features the Wasp, played by Evangeline Lilly, as a lead, alongside Paul Rudd as Ant-Man.

Marvel has started to embrace representation in both its cast and crew, shown most notably in Black Panther in February. While the first and second phases of the MCU were overwhelmingly white and male, the studio has been recently stepping up to increase the diversity of people both on and off-screen.
This could be Scarlett Johansson’s 8th time playing the role. She appeared so far in Iron Man 2, The Avengers, Captain America: The Winter Soldier, Avengers: Age of Ultron, Captain America: Civil War, and Avengers: Infinity War. We will see her again in the untitled fourth Avengers movie in May 2019. It is possible she will cameo in Ant-Man & the Wasp (July 6, 2018) or Captain Marvel (March 8, 2019), both of which take place before the events of Infinity War.
Source: Deadline
Seeing as a director still is yet to be confirmed, a release date is far away for the Black Widow solo film.
There is currently no plot synopsis for the film either, but some fans speculate the film will serve as a prequel.