There will be custom outfits that you can purchase in microtransactions.
For those worried that it will include gameplay altering mechanics, lead combat designer, Vincent Napoli, clarified they will not.
There are other aesthetic ways to customize your player card and your player experience, but there is nothing that affects the gameplay.
As of right now, no one knows if these custom outfits will be the only microtransactions. Marvel’s Avengers is coming out May 15, 2020 to the PS4, Xbox One, PC, and Stadia.