Screenwriters Stephen McFeely and Christopher Markus hinted at a possible plot point for the third Captain America film. In an interview with Den of Geek they dropped a hint when Markus said, “All I’m saying is psychotic 1950s Cap.” Marvel aficionados interpret that to be a reference to William Burnside who took up the Captain America mantle following the disappearance of Steve Rodgers. He was injected with an incomplete version of the Super-Soldier serum which caused psychotic symptoms.
While not confirmed by Marvel, reports indicate that the 3rd Captain America film will be released May 6, 2016.