So as we know normally the MCU movies and series are mainly set in real time, meaning that the movies and shows are set within the same timeframe as they are released (ex:
Age of Ultron is set in May 2015, while
Ant-Man is set 2 months after the events of Ultron in July 2015, the same year and month both films were released).
But it looks like
Guardians of the Galaxy Vol 2 will be joining the
Iron Man trilogy,
The Incredible Hulk,
Jessica Jones Season 1 and
Daredevil Season 2, as just like these movies and shows,
Vol 2 is not going to be set in the same month as its release date, it wont be set in 2017 to begin with. James Gunn confirmed in his Facebook page, that the events of
Vol 2 will be set in 2014, just 2 months after the events of
Vol 1.
So if the original movie is set in August 2014 that means
Vol 2 will be set in October 2014, setting it before the events of
Avengers Age of Ultron, Since the Guardians will return for the upcoming
Avengers movies, how this may affect the timeline in regards to
Avengers: Infinity War and
Avengers 4 is yet to be revealed, but that does beg the question if Groot will be fully grown by
Infinity War then.