Marvel Studios has announced that Guardians of the Galaxy 2 will premiere May 5, 2017, up from the July 28th release date.
Marvel usually gives the month of May to their large blockbuster movies, such as The Avengers and Iron Man 3. Guardians of the Galaxy is actually the #3 movie at Marvel Studios to date, so giving the sequel a big May release date makes perfect sense.
"Hey everybody, this is James Gunn. I'm sorry I can't be there with you. I'm here in Tokyo, Japan serving as a jury member on the Tokyo International Film Festival. I wanted to let you all know, I am working very hard on the script for Guardians of the Galaxy 2. I'm very excited about the movie. So excited in fact, that I don't want to have to wait until July of 2017 for the movie to be released. I think we would rather release the movie in May of 2017. I think that sounds right. May 5th 2017 is the new release date for Guardians of the Galaxy 2, so that we can spend the whole Summer with you guys."
Gunn also added on Facebook:
Today we announced that Guardians of the Galaxy 2 is being released EARLIER, on May 5, 2017. Because I just can’t wait!
James Gunn also previously confirmed Guardians of the Galaxy 2 will see the returning characters of Peter Quill/Star-Lord, Gamora, Drax, Rocket Raccoon, Groot, some others from the first movie as well as introducing new characters.
It's also possible we may see the Guardians in The Avengers 3 and 4 as Marvel announced The Avengers: Infinity War Part 1 and Part II.