In the contemporary media landscape, where filmmakers are often more accountable to shareholders than to their muses, studios have become ravenous for franchises. The ability to present audiences with something both new and known is the ticket to profitability, and no ticket has ever been as golden as The Avengers.
The Avengers is the infinite franchise. The number of moving parts it has boggles the imagination. It launches a series that is itself the culmination or continuation of at least four other franchises. It is simultaneously the first film in a series and the sequel to five other films. Having already broken every available box office record, it will also undoubtedly be a launching pad for one or more spinoffs featuring ancillary characters and Avengers To Be Named Later, to say nothing of the resurrection of the Incredible Hulk series.
The result is a narrative daisy chain that alters, and to some extent potentially damages, each individual film's ability to legitimately begin, tell its story, and end. Iron Man, Thor, and Captain America have wildly different tones, settings, and even eras, but all must build on one another and lead into one another so that when Thor and Tony Stark finally do share a world, it is not jarring or ludicrous. One false move not only ruins The Avengers but tarnishes the legacy of the previous films.
To some extent, this type of filmmaking requires the viewer to be in for the long haul. Pepper Potts' and Tony Stark's relationship cannot develop in The Avengers because they need to "save it for their own movie." If you had the gall to leave Iron Man when the credits rolled, everything about Samuel Jackson is a non sequitur. Pity the poor soul who sees movies without reading about them online all year: "Am I crazy, or is this 'Coulson' character showing up in every movie we see?"
As monumental as this undertaking is, it has succeeded, meaning it will quickly go from being anomalous to being copied badly by every other studio in Hollywood. What will the long-term impact be? Will every summer movie come with homework and a reading assignment for the next decade? Is this the dawn of every film ending with ellipses and Easter eggs? Only time will tell, but I wouldn't tell any fans of auteur filmmaking to hold their breath.
On the plus side, maybe Edgar Wright can finally get Ant-Man made.