The deal is said to begin with Captain America: Civil War and to include Avengers: Infinity War Part 1 and Part 2. Throw in a Black Panther solo film in 2017 and you only have one more movie in the deal… likely a Black Panther sequel if the first film does well.
During the announcement yesterday when asked about casting of Carol Danvers / Captain Marvel, Kevin Feige said that there would be director and writer announcements before casting. They announced Boseman because he's going to appear in Civil War which has its writers and directors. Since we don't have a Captain Marvel then its safe to assume that she won't be making her first appearance until at least Guardians of the Galaxy 2 but more likely Avengers: Infinity War Part 1.