Rumors about additional members to join "The Avengers" have been circulating as a revamped "The Amazing Spider-Man" has also launched this summer, doing solid business. That situation becomes problematic in that Sony owns the rights to Spider-Man, whereas The Avengers and its entire roster of heroes is owned by Disney/Marvel. While the smart move for Sony would be to license out the web-slinger in exchange for a chunk of the gross, Sony isn't likely to do that, as the re-launching of Spider-Man is said to be the start of a new, self-contained trilogy, according to Yahoo, back when the film opened in July.
"Hurt Locker" star Anthony Mackie has signed on to the "Captain America" sequel, "Captain America: The Winter Soldier," playing longtime Avenger and agent of SHIELD, Falcon. This also seems likely that we'll be seeing Mackie in "The Avengers 2," standing shoulder-to-shoulder with the rest of the Avengers, taking on either Thanos (teased at the end of "The Avengers") or, since Marvel has recently re-acquired the rights to its most powerful celestial adversary, Galactus.
As Marvel has regained the rights to Galactus, it has also regained the rights to the Silver Surfer, a known cosmic entity who has crossed paths with The Avengers in the past. The Silver Surfer was last seen in 2007's "Fantastic Four: Rise of the Silver Surfer." The theory behind a more cosmic showdown with Galactus is backed up by the fact that in "Thor: The Dark World," the story is said to involve the realm of Asgard, home of Thor and the Warriors Three. The main villain will be Malekith the Accursed, played by British actor Christopher Eccleston. Thor has always been somewhat of a cosmic character, as he is, after all, a god. Squaring off against an enemy like Galactus would pose a serious threat to the galaxy as a whole, and would certainly raise the stakes of the original film, which saw The Avengers facing an alien invasion led by Thor's brother, Loki.
The next big Marvel intellectual property to his the screens is the very strange and cosmic "Guardians of the Galaxy," which is rumored to have Thanos, the enemy teased at the end of "The Avengers" as its main villain. How the general moviegoing public will react to characters like Rocket Raccoon, Drax The Destroyer or Groot (who is part tree) is a different story. With screenwriter Chris McCoy handling scripting duties, it seems strange to waste such a powerful villain like Thanos on a group of second-stringers like the Guardians of the Galaxy. In "The Avengers", the Chitauri leader says to the to-be-revealed Thanos that challenging humans is "to court death", a reference to Thanos' quest to obtain The Infinity Gauntlet, an all-powerful gem-powered device. An actual prop of The Infinity Gauntlet exists and was seen at the 2010 Comic-Con in San Diego, so it's natural to assume it'll pop up on-screen at some point, perhaps as the weapon to rival the combined might of The Avengers.
Fox has retained the rights to Daredevil, the blind lawyer-by-day who becomes a senses-enhanced crime fighter at night. Last seen on-screen in 2003, starring Ben Affleck in the lead, the series is getting dusted off by hot director Joe Carnahan, fresh off "The Grey." The chances of Daredevil appearing in The Avengers 2 are slim, however; Fox (unlike Sony) might be more apt to lend out their hero stable (which also includes The Fantastic Four), should Marvel find a use for them. The main concept at play would be free money for use of intellectual property. As of right now, there's no Daredevil trilogy planned, so that would potentially leave the lead actor and producers open to using the "man without fear" in "The Avengers 2."