Robert Downey Jr.'s ubiquity these days is unrivaled as it appears the 49-year-old actor has joined the cast of "Captain America 3," reprising his role as Tony Stark and Ol' Shellhead, Iron Man.

It's also reported that Marvel Studios is adapting and/or rebooting the 2006 Mark Millar-penned "Civil War" comic event.

Variety states that Downey is in final negotiations to be featured in "Captain America 3," which is slated to begin production this spring for a May 6, 2016 release starring Chris Evans.

It's said the plot for "Captain America 3" will pit Tony Stark/Iron Man against Captain America/Steve Rogers as they feud over the Superhero Registration Act, which forces anyone with superhuman abilities to register their identities with the U.S. government, and also agree to act as a police force for the authorities. In the comics, Captain America was anti-registration while Iron Man was pro-registration.

It's indicated that due to the moral dilemma of registering vs. not registering, Downey's Tony Stark will be looked at as a villain of sorts in "Captain America 3," which could play out in "The Avengers 4" as well.

Downey has been teasing more from Iron Man, and has made various, sometimes conflicting statements about the franchise on his current PR tour for "The Judge." The article states that Marvel initially wanted Tony Stark for a smaller role in "Captain America 3," but Downey wanted Stark/Iron Man to have more of a substantial role (which actually fits with the comic book storyline). Obviously, more time for RDJ means better pay for the actor, which is said to have angered billionaire Marvel CEO Ike Perlmutter, who is also rumored to be at odds with Fox Studios over the film rights to the "X-Men" and "Fantastic Four" properties, with Perlmutter reportedly ending the use of the characters in the Marvel Comics.

Purportedly, Marvel Studios president and producer Kevin Feige was the one who saved the deal from going sour, as Feige envisioned keeping the characters around for the long haul. It seems as RDJ is so close to signing that Feige convinced Perlmutter not to order the screenwriters to write Downey out of the script, which is what Perlmutter originally intended.

The piece also states that the "Civil War" storyline will be used as way to drive the plots of sequels and new franchises for the Marvel Studios movies for the next seven years, which is why Feige wants Downey involved.

The fallout from the "Civil War" storyline and Tony Stark's actions is said to be a factor leading into "The Avengers 4" and beyond, with mention of assembling new characters like Ant-Man and Doctor Strange in their own movies.

Downey's deal for "Captain America 3" is to include a hefty $40 million payout plus bonuses if the film outperforms "Captain America 2," which netted $714 million for Marvel.

It is also worth noting that Warner Bros. recently backed its "Batman Vs. Superman" film away from a head-to-head summer box-office showdown with "Captain America 3," and now with Downey seemingly just about signed, that doesn't seem like such a bad move on the part of WB.

This news comes almost directly on the heels of Marvel Comics announcing a new "Civil War" event for the summer of 2015.