To call The Conjuring the horror movie hit of 2013 (so far) would be quite fitting. Director James Wan's R-Rated supernatural scarefest has already grossed more than six times its $20 million budget worldwide in theaters - in addition to earning critical kudos, for old-fashioned spooking tactics and Wan's technical expertise. New Line Cinema gave the go-ahead for development on a sequel before Wan's film began its theatrical run; needless to say, the studio's instincts were right on the money (in this case).
WARNING: MILD SPOILERS FOR THE CONJURING AHEAD
The Conjuring was loosely - emphasis on loosely - inspired by one of the real-world cases that involved the paranormal investigator/demonologist husband-wife team of Ed and Lorraine Warren (as portrayed by Patrick Wilson and Vera Farmiga in the movie). Wan's film concludes with Ed briefly mentioning to his significant other that he's been informed about a potential new case in Long Island - a reference to the real-life incident that inspired The Amityville Horror (which ended up being investigated by the Warrens).
However, according to AICN's source - who claims to have attended "an intimate gathering at Lorraine Warren’s home" recently - that case will not be the basis for the Conjuring sequel plot:
The case file they’re looking at [occurs] in the late '70s and centers on two sisters in Enfield, England, who were allegedly possessed. Warren said she personally saw them levitate and even saw one of the sister dematerialize in front of her only to be found 20 minutes later stuffed into an oversized fuse box, contorted in such an unnatural way that they couldn't have replicated it if they tried. She also said that the demon spoke directly to her husband on many occasions. Warren cited this case as one of the most terrifying experiences of her career.
Truth be told, it wouldn't make a whole lot of sense for The Conjuring sequel to focus on the Amityville incident, which has been so heavily dramatized and re-told onscreen in the past. Not to mention, a recounting of that event from the Warrens' perspective might have trouble bringing an interesting and refreshing dimension to the proceedings. On the other side of the coin, a case like the one described above - one of several lesser-known occurrences that involved the Warrens - offers ripe material for a screenwriter to adapt - by letting their imagination run wild with the "truth" behind it all.
Carey W. and Chad Hayes' script for The Conjuring definitely has an anecdotal feel; in some ways, the three-act narrative resembles that of a glorified pilot episode for a TV series (in ways good and bad), which follows the Warrens as they investigate a terrifying new case every week. You can see already see how the rumored story for Conjuring 2 - with the Hayes twins back as the screenwriters - could pickup the story threads left dangling in the first movie - like the emotional toll that each demonic encounter takes on the clairvoyant Lorraine.
That said, if Wan doesn't return as the director on The Conjuring sequel, then it'll be more than a little difficult to get fans of the first installment onboard for Part 2 - regardless of whatever the plot winds up being.