Minor spoiler warning...
Avengers: Infinity War screenwriters Christopher Markus and Stephen McFeely had a lot on their plate when crafting the narrative of the film and its still untitled sequel, which necessitated backburnering some characters such as Hawkeye and Ant-Man, and waiting for Avengers 4 to give characters like Steve Rogers and Black Widow their big moments.
“Some of the people, when you weigh up who you are seeing, seem to take a little bit of a back seat in this one,” Markus told The Hollywood Reporter. “When we did crack them, what we realized was they had far more potential in the movie coming next year, just in terms of how their character would be tested by the story. I'm not telling you what the story is.”
“I will say there is less Steve Rogers and Natasha (Scarlett Johansson) than you might expect in this movie,” he continued. “Because they are such hard-bitten people, when a threat comes, they stand there and they take the threat. They don't crack. They don't whimper. They don't start talking about all their failed opportunities. So, there isn't that much to explore, especially when you don't have a lot of time. But there's a lot later.”
“We cracked them both together, so we had to give ourselves permission to say that some people are going to get more in the next movie,” added McFeely.
As for Ant-Man, he's got his own solo film coming up in just a few months, freeing the writers up to focus on other characters. But that doesn't mean Ant-Man and the Wasp won't factor into the overall Infinity War story.
“When we get to this time next year, all will become clear,” explained McFeely. “Ant-Man clearly had a specific requirement, which is he had an entire movie that is going to come between these two movies. Same thing with Captain Marvel, by the way. We looked at that as an opportunity, not as some sort of back-bend we had to do.”
“Also, Ant-Man the franchise is very light-hearted. It's fun. It maybe even skews younger,” added Markus. “If we were to put Ant-Man in this extremely heavy movie, and then have to say to the guys who are making the Ant-Man movie, 'Yeah, he went through hell, but now go ahead and have your little romp and we'll pick it up afterwards,' that's why we have to really sort of manage your interconnections and go, ‘Let's go and hold off so you can enjoy that without feeling a bad taste in your mouth.’"
Avengers: Infinity War is in theaters now. Its untitled sequel is due out May 3, 2019.