Black Widow was assumed to be Scarlett Johansson's last outing in the MCU. After all, the prequel was Natasha Romanoff's final appearance since she already died during the events of Avengers: Endgame. But as it turns out, that wasn't the last time that Johansson is involved in the MCU.
According to Deadline, during an event where Johansson was honored with the American Cinematheque Award, Marvel Studios head Kevin Feige was in attendance in which he gave a speech praising the actress. Then, he revealed that Johansson is working on a "top secret Marvel Studios project" that has nothing to do with Natasha Romanoff where she will serve as the producer.
Feige said in his speech, "Scarlett has lent her talent and star power to the Marvel Cinematic Universe for over a decade. That she’s chosen to play a key part in it for so many years, I am extremely grateful for. Working with [her] has truly been one of the most memorable and rewarding collaborations of my career."
However, Johansson's lawsuit against Disney (which was settled recently) wasn't addressed during the event. The actress' MCU colleagues such as Jon Favreau, Chris Evans, Robert Downey Jr., Jeremy Renner, and Samuel L. Jackson also gave a speech paying tribute to her.
A lot of people are now wondering what "top secret" project is Johansson involved with. If you look at the upcoming Marvel Studios projects that were announced, there is nothing of it that sounds like Johansson would be closely involved in it.
There are fans who are speculating that perhaps it's an all-female Avengers movie since there are some who have been clamoring for it thanks to the particular sequence in Avengers: Endgame. However, we can also guess that Marvel may be working on a Yelena Belova solo movie or spin-off series which sounds like something that Johansson would definitely be involved in and help develop the next iteration of Black Widow in the MCU.
We should be hearing soon enough regarding more details on the top-secret Marvel Studios project that Johansson is working on.