After Captain America: Civil War, Black Widow will presumably return in the Avengers: Infinity War movies, but it hasn’t been confirmed if she will appear in any of the other Marvel Phase 3 movies aside from that.
It will likely be quite some time before the studio is ready to announce which movies will take those 2020 release dates, but Black Widow could certainly be one of these Marvel Phase 4 movies.
Last month, Kevin Feige teased that he would still love to see a Black Widow movie in the MCU, but he doesn’t think it would happen until at least 2020, in Marvel Phase 4.
We’ll be sure to keep you posted with more on the potential Black Widow movie as soon as details are announced.