It's the day that Marvel Comics fans have been waiting for. With the future of the Marvel Cinematic Universe unclear after the impending arrival of Thanos the Mad Titan, it seems Captain America 3 will not only tell the next chapter in Steve Rogers' (Chris Evans) life, but will be bringing in Tony Stark (Robert Downey, Jr.) as well - to begin the universe-wide start of Civil War - an adaptation of the 2006-2007 comic book event.

The report comes courtesy of Variety, claiming that Downey is in final negotiations to join Captain America 3, and citing the 'Civil War' comic event as the foundation on which the film will be built. With the proposal of the Superhuman Registration Act, the superhero community of the Marvel universe is split in two: those believing that superpowered individuals should be registered and trained and standing with Tony Stark, and those standing in opposition with Captain America.

The core series written by Mark Millar dealt with the rivalry, covert war, and eventual confrontation between Stark and his allies - those fighting for national security - and those of Rogers - who believed that civil liberties were more important. According to Variety's sources, the event could only exist - as envisioned by producer Kevin Feige - with Downey, Jr. signed for a large role (given the source material, that's not surprising). And in recent weeks, disputes between Marvel's higher-ups put the deal's existence in jeopardy. At this point, the Iron Man star has more than earned his right to demand top dollar.

Downey, Jr. (who earned $50 million for his role in The Avengers) is reportedly set to take home $40 million for his role in Captain America 3, with an extra bonus if the film outperforms Captain America: The Winter Soldier's box office take. In recent weeks, Downey, Jr. has been somewhat elusive in his claims that plans were in place for Iron Man 4, later backtracking on those statements. Now, it's clear why he avoiding confirming or denying his role in the next phase of the Marvel Cinematic Universe.

The Avengers 2: Ultron with Captain America and Iron Man

The idea of Marvel relying on such a far-reaching and universe-wide story may send fans reeling, but it's been pointed to for some time as a likely means of catapulting new characters and franchises in the wake of both The Avengers: Age of Ultron and the arrival of Thanos (James Brolin). And to this point, Marvel has been moving many of their key pieces into place for doing 'Civil War' justice. When Winter Soldier directors Anthony and Joe Russo claimed that Captain America 3's subtitle alone would have a major impact, hopes for a 'Civil War' event were bolstered further.

With Iron Man 3 leaving Tony Stark questioning the need for his Iron Man armor, and with Age of Ultron presumably putting the blame for the villain's creation on his shoulders alone, he's set to make some tough decisions. In terms of 'Civil War,' those same doubts and uncertainty led Stark to decide that a Superhuman Registration Act - outlawing those who acted as brashly with their gifts as he did - was the only solution.

With the cinematic version of Steve Rogers coming to realize that government surveillance has its downside, and ruling that sacrificing privacy and freedom for the sake of national security was a bargain not worth making, he's done and said all he needs to become the face of those opposing Stark's stance. But the feud between the two men may be even larger than some fans expect, given the film's 'Captain America' title.

Marvel Comics Civil War Crossover

Additional details have come from sources of BadassDigest, claiming that the team of Cap's new Avengers assembled at the end of Age of Ultron - possibly Falcon (Anthony Mackie), War Machine (Don Cheadle), Quicksilver (Aaron Taylor-Johnson), Scarlet Witch (Elizabeth Olsen) and Black Widow (Scarlett Johansson) - could also appear alongside the film's two co-leads, Stark and Rogers.

As one might expect in a film where the two most established leaders of the Avengers universe are no longer allies, but political opponents, Captain America 3 will leave the entire stability and future of the Marvel Cinematic Universe in question. It's because of this uncertain status that, as prior reports have claimed, The Avengers 3 may not include the most well-known members of the super-team.

Just how long it takes for the world's heroes to get back on their feet - and those who read the comics know which of the two men ends up victorious - isn't clear, but with Earth's mightiest heroes at war, even an uneasy truce will present a much more vulnerable target for Thanos to attack, either in The Avengers 4 or beyond. If those reports are true, then Thanos still has several years of plotting (and potential cameos) ahead of him.

Marvel Movies Civil War

The site also claims that the title of the film may actually be 'Fallen Son,' not 'Civil War' - possibly alluding to the comic circumstances that once led to Captain America giving up his title and shield for a time. Whatever the case, taking 'Civil War' as the event which the immediate future of the Marvel universe is building to helps several odd bits of news or rumor make a bit more sense; not the least of which was the confusing announcement that Marvel Comics was re-launching 'Civil War' in 2015.

Since Peter Parker played a pivotal role in the comic event, forever changing his place in the Marvel universe, the recent rumors that Sony may be rethinking its stance on a crossover make perfect sense. The Spider-Man movie brand is in need of a jump-start, and involvement in an event of this size would certainly do the trick.

On a smaller scale, the sheer number of characters caught up in the storm of the Superhuman Registration Act opens up several doors for the street-level heroes of Marvel's upcoming Netflix slate, beginning with Daredevil. It's entirely possible that as the feature films raise the stakes higher than ever before, characters like Luke Cage, Jessica Jones, or Iron Fist could help root the conflict in more familiar settings.

Marvel Movie Civil War Spider-Man

The event raises just as many questions as its apparent announcement answers. Where does this leave the future of Agents of S.H.I.E.L.D. - and with whom would Coulson's team side? Could some time away from the movies help to re-establish a lasting relationship between Marvel and star Chris Evans, or end it? Hopefully those questions and more will be answered in the coming months.

We'll keep you updated as more news or an official confirmation or comment from Marvel arrives. For now, share your thoughts (and excitement) in the comments.

Captain America 3 (Civil War?) is scheduled to release on May 6, 2016.

Follow me on Twitter @andrew_dyce for Captain America 3 updates as well as movie, TV and gaming news.

Source: Variety, BadassDigest