Although Marvel has yet to announce the line-up for their slate of Phase 4 movies, everyone is aware that Black Widow is currently filming. It's hard to keep anything a complete secret these days, especially with the amount of Marvel fans in each country. Black Widow is busy filming outside the country, but still, photos from the set taken by curious on-lookers keep hitting the web. A recent leaked set photo appears to reveal a new hero that will be entering the Marvel Cinematic Universe.
Black Widow will star Scarlett Johansson and Florence Pugh, the latter of which appears in an undisclosed role. Her role has now been discerned. The leaked set photos show a shot of Johansson and Pugh's characters riding a bike, but the lifelike heroes are actually dummies being used for an action sequence. The dummies look real, but what is more intriguing is the boxes they came in. One box in labeled "Natasha" for Black Widow while the other is labeled "Yelena."
For those who may not read the comic books, Yelena is a spy that takes on the mantle of Black Widow when Natasha steps down from the role. They start off as enemies, but become close friends. It is possible that the MCU is setting things up to introduce a new Black Widow to replace Natasha since she died in Avengers: Endgame.