Given that there is still a bit of time before Avengers 4 is released, there is one thing that can be looked at. This is the possibility of characters that could be included in the upcoming movie. One thing that has been stated about Avengers 4 is that it is going to deal with the cosmic aspects of the universe. This could bring forth characters such as Eternity, Infinity, and other conceptual entities. Of course Thanos is going to return in Avengers 4. After all, the story is going to be based around the incident that occurred in Infinity War.
One thing that the creative team behind the Avengers movies have said is that Avengers 4 isn’t going to undo everything that happened in Infinity War. Therefore, there is a lot of speculation about what might happen with Avengers 4. One clue to look to is the upcoming films and what has been revealed about the films. Both Black Panther 2 and Spider-Man Homecoming 2 has been confirmed to take place after the events of Avengers 4. This means that some of what has happened in Infinity War is going to be undone. However, it has also been revealed that there are going to be sacrifices made.
Another new character that could appear in Avengers 4 is Captain Marvel herself. She might be the key to stopping the Mad Titan. In the comic book, it was Adam Warlock, but he is not going to appear until Guardians of the Galaxy 3. It is possible that Captain Marvel is going to take on the role that Adam Warlock has played in the comic book version of the story.