Robert Downey Jr. is in negotiations to join the cast of Captain America 3. The film would center on Marvel’s popular Civil War story arc from 2006.

Marc Graser at Variety, who broke the news says, ” The new pact is significant for the Marvel cinematic universe considering the plot will pit Stark against Captain America’s alter-ego Steve Rogers, played by Chris Evans, as they feud over the Superhero Registration Act, which forces anyone with superhuman abilities to reveal their identities to the U.S. government and agree to act as a police force for the authorities.”

Now there’s a lot of tweaking that needs to go on if this is to be the case. For one, the movie rights for Spider-Man and The Fantastic Four, who play a role in the comic version of Civil War, are not owned by Marvel. This isn’t a huge set-back for Marvel though as they have proven capable of tweaking their movie adaptations successfully – inserting Black Widow into the most recent Captain America movie being the perfect example.

Downey already has a massive deal to appear in Avengers 3 and the rumored payday for his Captain America 3 appearance is $40 million plus a piece of the back end, plus an additional bonus if Captain America 3 outperforms Captain America: The Winter Soldier‘s $714 million worldwide haul. In other words, Downey could easily make upwards of $80 million plus on a third Cap movie.

Graser reports that the deal for Downey almost didn’t happen. (That could point to the waffling he did on a couple of talk shows last week) Marvel had wanted to hire Downey for a small role but Downey wanted Stark to have a larger role in the film’s plot which would give him more screen time and consequently a bigger payday.

That move angered Marvel Entertainment chief Isaac Perlmutter who ordered screenwriters to write out Iron Man from the script entirely. Though the deal appeared dead, Marvel Studios president Kevin Feige and Downey’s reps continued to meet to work out their differences.

Marvel has been a tough negotiator since entering the movie world. Some would even say they’ve been cheap, but the studio hasn’t been shy in paying Downey what he’s asked for after he helped launch the Marvel Cinematic Universe with the first two Iron Man movies. Downey has reaped nearly $300 million from the three Iron Man films, The Avengers and his cameo in The Incredible Hulk.

To help suck in new fans, Marvel announced that they would also be rebooting their Civil War comic book miniseries in 2015.

That’s not all that is going on in the Marvel movie world though. Devin Faraci at Badass Digest reports that the Russo Brothers are the rumored front-runners to direct both Avengers 3 and 4. (I know, this MCU is never going to end)

The Russos directed Captain America: The Winter Soldier and are set to direct Captain America 3 and Marvel president Kevin Feige has been full of praise for the Russos since they signed on.

There still plenty that will occur before Captain America 3 arrives in theaters including the introduction of Ant-Man in his solo movie and of course, Avengers: Age of Ultron next summer. For the latter, expect a teaser trailer to appear soon and be attached to Disney’s Big Hero 6. If you can’t wait that long, here’s a brief description of the trailer from NYCC this past weekend.