On Sunday he "hinted" at what's in store for the next film.
Captain America: Civil War picks up where Marvel Avengers: Age of Ultron leaves off.
The collective governments of the world pass an act designed to regulate all superhuman activity. This polarizes opinion amongst the Avengers and Captain America is forced into conflict against former allies.
In addition to Downey, the film stars Chris Evans as the titular super soldier and Chadwick Boseman. Directed by Anthony and Joe Russo, Civil War is scheduled to hit theaters May 6, 2016.