Marvel has now officially confirmed that report the other week that "Captain America 3" is currently targeting a May 6th 2016 release - the same day as Warners' much-hyped "Batman vs. Superman".
The film's screenwriters Christopher Markus and Stephen McFeely also recently spoke with Collider and say that the film is a bit further along than you may have thought.
Though still in the early days of the script, the pair have been working on the project since late last year. Ideas are being thrown around and tested, and it's "coalescing into the movie it's supposed to be". They've also read Joss Whedon's "Avengers: Age of Ultron" script and are happy with where Captain America is when the film ends.
At present, they don't know how big of a role the Winter Soldier will have in the third film and they want to make sure no-one overshadows the Captain himself. They've also deliberately setup some threads in 'Winter Soldier' that they intend to continue on with.