I posted the above 5 days ago. Since then, a few things have happened.
1. Marvel announced that there plan is to do at least one sequel and one original film every year.
2. Robert Downey, Jr. announced he's open to doing Iron Man 4.
3. Star Wars VII actor John Boyega tweeted this:
4. Marvel announced today that they're adding May 4, 2018 to the roster. Apparently, The Amazing Spider-Man 4 is slated for that date as well.
So based on that, I'm changing some of my guesses for the upcoming slate. I doubt Downey or Boyega would make those comments unless Marvel is planning on announcing Iron Man 4 and Black Panther at Comic-Con.
May 1, 2015 - Avengers: Age of Ultron
July 17, 2015 - Ant-Man
May 6, 2016 - Captain America 3
July 8, 2016 - Doctor Strange
May 5, 2017 - ??? (Iron Man 4)
July 28, 2017 - ??? (Black Panther)
November 3, 2017 - ??? (Thor 3)
May 4, 2018 - ??? (Avengers 3)
July 6, 2018 - ??? (Captain Marvel)
November 2, 2018 - ??? (Guardians of the Galaxy 2)
May 3, 2019 - ??? (Avengers 4)