Major Avengers: Endgame spoilers ahead. It was clear going into Avengers: Endgame that it would be some sort of goodbye to the original group of Avengers, who first team up in 2012's The Avengers. It was how that would shake out that was less clear. And when it comes to Black Widow's fate in Avengers: Endgame, we now know how things turn out for Scarlett Johansson's character Natasha Romanoff. As for what this means for Black Widow's Marvel Cinematic Universe future, well, it definitely could have an impacted on her reported solo movie.
The film is the end of an era, and some of the stars' contracts were up, but that didn't necessarily mean that all six original Avengers would be killed off. But, it was expected by most fans that there might be a couple deaths, and Black Widow's ending up being one of them.
Natasha's death comes in the latter half of the movie, but long before the final epic battle between the Avengers and Thanos. (Yep, again.)
The Avengers' goal in Endgame is to go back in time and collect all of the Infinity Stones before Thanos does, so that they can stop his murderous snap from ever happening. The group splits up, with different heroes meant to collect different stones, and Black Widow and Hawkeye travel to the planet Vormir to collect the Soul Stone.
The problem is that to retrieve the Soul Stone, a soul must be sacrificed. (This is why Thanos sent Gamora to her death in Avengers: Infinity War.) Hawkeye wants to sacrifice himself and Black Widow wants to sacrifice herself, and they end up battling it out over who it's going to be, with both of them attempting to run towards the end of a cliff to jump over. Eventually, with them both hanging on to each other for dear death, Black Widow ends up being the one to fall, leaving Hawkeye to collect the Soul Stone and travel back to the present without his partner.
During their conversation about who it should be, Black Widow explains that while Hawkeye has a wife and children who would return if the Avengers are successful (his family disappeared due to Thanos' snap), her family was the Avengers and she'd made it her life's purpose in the five years since the snap to undo it. As shown earlier in the film, while some of the Avengers had tried to move on post-snap, Black Widow remained at Avengers HQ, checking in on everyone and trying to find a solution. She also took the Avengers' message of "whatever it takes" very seriously and that included falling willingly to her own death.
Now, to step away from the movie, what made this particular death surprising, even though some deaths were expected, is the fact that a Black Widow movie is reportedly in the works. According to The Hollywood Reporter, it will start shooting this June, though Johansson hasn't commented on it herself. The fact that Black Widow dies in Endgame makes it seem that her standalone movie will be a prequel. That along with this description THR reported, "[I]t will be an internationally set story centering on Natasha Romanoff, a spy and assassin who grew up being trained by the KGB before breaking from its grasp and becoming an agent of S.H.I.E.L.D. and Avenger."
Of course, superheroes can return from death (Endgame is all about that), but this one felt much more final. Plus, a prequel would make sense for Black Widow: We haven't seen her origin story yet, but it's clearly what led her to be the way she is.
As Entertainment Weekly explains in its "hero-a-day countdown" feature focused on Black Widow,
"With Avengers: Endgame promising resolution for the classic heroes, the redemption she has sought for herself as a former Russian assassin may finally erase the red from her moral ledger. What were those past wrongs? We can only imagine — based on the level of heroism and self-sacrifice she has displayed to tip the scales back."
Well, in Endgame she literally sacrifices her entire life, so perhaps her movie will show what she went through that would lead her to do that and to make the other decisions she does in the Avengers films.
With Endgame in theaters, it probably won't be long now until Johansson can comment on her (potential) movie, and until fans find out when and how they'll get another look at Black Widow.