Marvel's supervillain Crossbones, who was played by Frank Grillo in Captain America: The Winter Soldier and Captain America: Civil War, is speculated to return to the MCU in 2019's Avengers 4, despite being presumably killed in Civil War.

While not officially confirmed, Robert Downey Jr who plays Iron Man in the MCU took to Instagram to share an image of actors Scarlett Johansson, Chris Evans, Jeremy Renner, Mark Ruffalo, and Danai Gurira, along with Frank Grillo, which was shot behind the scenes of the metatheatrical three-act play Our Town.

This isn't the first time the return of the rogue Hydra agent has been hinted at. Grillo himself, in a recent interview, said: “I was surprised not too long ago, because there is some news that nobody knows yet, to do with my character, that’s going to be really interesting and I’m excited about that.”