http://www.ign.com/articles/2013/08/07/marvel-studios-has-movies-planned-up-to-2021

"I could arguably say what we're planning for the year 2021," Marvel Studios President Kevin Feige said in an interview with WIRED. "Will that happen? I don't know. But what we planned for 2015 in 2006 is happening."

Three release dates have already been announced for unspecified movies -- two in 2016 and one in 2017 -- and now we can expect even more in the upcoming years. Characters such as Doctor Strange and Black Panther are rumored to have movies in development, but with 50-plus years of comics to fall back on, Marvel could go any direction.

"Five years ago, looking at our plan, we knew that if Avengers was going to work, the movies had to stand alone," Feige said. "Now we have to prove to the studio that we're more than just these five characters, these five franchises."

With 2014’s Guardians of the Galaxy and 2015’s Avengers: Age of Ultron, Marvel Studios will have completed Phase 2 of the Marvel Cinematic Universe. They are immediately launching Phase 3 with the long-gestating Ant-Man movie the same year as the Avengers sequel, so if they continue their current pacing, they’ll be in Phase 4 by 2021. What will the MCU look like then?