Marvel's Grand Plan for its MCU is moving through its phases quite nicely. But if there was one critique that still hasn't been dealt with, it's the lack of concrete female heroes and a more in-depth look at their respective back stories.
For starters, Black Widow, who has been both Avengers movies and even Cap's own solos, it seems that she can't get a break in getting her own. And it's far from fair, to be honest, given that heroes who were introduced later on, including Black Panther, Doctor Strange, and even Spider-Man already have their own solo exploits.
Her fellow Avenger, Captain America a.k.a. Chris Evans hasn't given up on the possibility of Black Widow's own movie. In an interview (via CBM), Evans gave his two cents' on how he thinks that movie is just something waiting to happen:
"That's a good question. It would really just clean up, wouldn't it? Scarlett [Johansson] is so good at everything she does. She's played such a crucial part in the other films. She always makes her presence so felt—even when there are 50 different superheroes running around onscreen. I wouldn't be surprised if that happens at some point in the future. I'm sure Scarlett would be open to it."
Granted, this is far from an assurance that a Black Widow movie could actually happen. Nothing is really in the hands of the actors after all, and Kevin Feige and the other execs at Marvel are charged with those decisions. But exploring her backstory—which we already got a glimpse of in Avengers: Age of Ultron—doesn't seems like it can go to a good place if they ever pursue it.
For now, we can wait for a female superhero-led movie with Captain Marvel, set to premiere in theaters in 2019.