Marvel was one of the first studios to delay their 2020 blockbusters, when they bumped Black Widow from May 1, 2020 to November 6, 2020.
As for Black Widow, expect the 2020 delay treatment should the theater situation not improve over the spring.
But they could soon run into an issue if their television shows come out and their movies do not.
Marvel was finally able to start Phase Four of their cinematic universe — which was originally scheduled to begin with Black Widow — with their new Disney+ series WandaVision.