It has been confirmed that the next Avengers film will be called Avengers: Infinity War.
The title suggests that this will be based on the massive Marvel Comics Crossover from 1991. The miniseries shows most of Marvel’s Heroes uniting again Thanos who has assembled the 6 Infinity Gems and gained godlike powers. The gems control Time, Space, Mind, Soul, Reality and Power and if you’ve been following the MCU closely enough you should have noticed a few in the various films.
There is no official title for Part Two yet, what we do know Anthony and Joe Russo will be back for both after directing Captain America: Civil War (which was really another Avengers film despite the title) though we don’t know plot details at this point but it seems there is a chance for a cameo from the newly cast Captain Marvel (Brie Larson).