Check out Joe Russo's comments below.
"That is another one that we would have to reserve as a surprise, but we will say this: People will not be disappointed in the amount of characters in the movie. The concept of Infinity War is that the Marvel universe unites to battle the greatest threat to the world and universe that you've ever seen, and we're going to honor that concept."Russo also talked about how Avengers: Infinity War Part One and Two will be realistic, while still having fantastic cosmic elements.
"We also are going to work really hard to bring a psychological realism. We obviously can't bring a naturalism to it because it doesn't really exist outside of science fiction, but we can bring that psychological realism to it, to the characters, and that's going to be our focus."Movieweb has more below.
'Avengers: Infinity War' Will Unite the Entire Marvel Universe