On Tuesday, Variety reported Robert Downey Jr. is in final negotiations to reprise his role as Iron Man in "Captain America 3."
The film is expected to follow the events of the Civil War comic books in which the two heroes clash over a law asking superheroes to reveal their identities and register in a government program.
Expect to see Iron Man vs. Captain America as they go head to head when "Captain America 3" hits theaters May 6, 2016.
"Avengers #29," Marvel Comics.
Why would Disney and Marvel add Iron Man and pit two of its most popular heroes against each other?
Disney needs to be able to hold it's own against Warner Bros.' hugely anticipated "Batman V Superman" film also out in 2016. It's a movie Warner Bros. tried to make in the early 2000s before scrapping it.
Warner Bros. originally set the date for its "Batman V Superman" film to July 2015 before pushing it back to May 6, 2016 - the weekend where Disney has previously released both its "Avengers" and "Iron Man 3" films. Both grossed over $1 billion at theaters.
Warner Bros. later decided to move the date of its superhero film up to March 25, 2016 to avoid going head-to-head with "Captain America 3."
Disney/Marvel, Rocksteady / Kirsten Acuna/Business Insider
While Disney and Marvel may very well have had this plan in play for a while (the Mouse House claims to have a schedule of Marvel films at the ready through 2028) there's another good reason to add Iron Man to a "Captain America" sequel.
Now that "Batman V Superman: Dawn of Justice" will hit theaters six weeks ahead of Disney and Marvel's "Captain America 3" they need a huge answer to Batman and Superman going toe to toe in a big action film.
Take a look at the box-office grosses of every live-action Batman film since 1989. With the exception of 1997's "Batman & Robin," the bat has always performed in theaters no matter what actor has donned the cape and cowl.
Box office Totals for Warner Bros.' Batman Movies
| Title | Year | Worldwide Box Office |
| "Batman" | 1989 | $411.3 million |
| "Batman Returns" | 1992 | $266.8 million |
| "Batman Forever" | 1995 | $336.5 million |
| "Batman & Robin" | 1997 | $238.2 million |
| "Batman Begins" | 2005 | $374.2 million |
| "The Dark Knight" | 2008 | $1 billion |
| "The Dark Knight Returns" | 2012 | $1.1 billion |
How do you compete with that? Feature your own superhero brawl between two beloved superheroes going toe to toe.
While Batman has always been a lucrative franchise for Warner Bros., Disney has the edge with another "Captain America" sequel for two simple reasons.
Audiences are more receptive to two characters - Robert Downey Jr.'s Tony Stark and Chris Evans' Steve Rogers - they've seen on screen for years now than to a Ben Affleck Batman who the jury is still out on and a Superman that received mixed reviews in 2013's "Man of Steel."
With Iron Man expected in the film, fans won't simply see "Captain America 3" as a sequel to "Captain America: The Winter Soldier" but also the "Iron Man 4" movie they've been asking for.
It's a win win for Disney's ongoing cinematic universe while Warner Bros. rushes to roll out superhero films to fast track two "Justice League" films in 2017 and 2019.