In terms of Marvel movies in the works, this year is expected to see the release of Black Panther, Avengers: Infinity War, and Ant-Man and the Wasp. This will be followed by Captain Marvel in 2019 and an untitled Avengers film in 2019. So far the only movie that was confirmed for 2020 is the Spider-Man: Homecoming sequel, but now it looks like Guardians of the Galaxy 3 can be added to that list.
https://twitter.com/JamesGunn/status/952350615476170752
It is expected for the most part that the original cast will return for the third movie, and it is also possible that Pom Klementieff might return in her role as Mantis, especially since she will be starring in the upcoming Avengers movie. Unfortunately details about the movie are scarce at the moment, but since we’re only in 2018, there’ll be quite a bit of waiting to do.
However with three Marvel movies planned for 2018, fans of the Marvel Cinematic Universe will have quite a bit to occupy themselves with.