They've battled monsters, lost friends, found love and made their creators a cool $6 billion (Dh22b), but Harry Potter and his magical pals have only one more film left in which to brandish their wands in the name of good versus evil. After Harry Potter and the Deathly Hallows Part II comes out in July, the most successful film franchise ever will be no more - but what's going to fill the gap?
Stephenie Meyer's Twilight saga, of course, is helping to pass the time between Potter films for fantasy-loving teens, and the film adaptations of the first two stories about high-schooler Bella and her love for a vampire have seen almost Potter-size box-office returns. The first instalment, Twilight, made almost $385m worldwide, and its sequels, New Moon and Eclipse, broke opening-day records in the US.
Sadly for Team Edward fans, though, there's only one more book in the series to adapt, although, like Harry Potter and the Deathly Hallows, it's being split in two to eke a few more bank notes out of the pockets of teenagers around the world. Part I will come out in 2011, with Part II being released the following year. Producers at the big studios must already be panicking about what to adapt next in order to get teens queuing at the cinema and falling in love with the big-screen versions of their favourite characters.
The front-runner for the Next Big Thing in teen movie franchises is The Hunger Games trilogy, a series of young-adult books by the American sci-fi writer Suzanne Collins. Darker and smarter than both Twilight and Harry Potter, the series is set in a dystopian future in which children are picked every year to fight in a televised gladiatorial death match. One of these kids is the series' 16-year-old heroine Katniss Everdeen, who, while she's not being shot at or stabbed, is torn between the love of two boys: a tough hunter, Gale, and a sweet-natured baker's son, called Peeta.
The series has all the ingredients for enduring success - doomed romance, high-octane adventure, a young protegť battling to save an entire community from evil - and it's spent 60 weeks on the New York Times bestseller list. Lionsgate has bought the film rights, and all Hollywood's teenage actresses are fighting to be considered for the starring role.
Thirteen-year-old ChloŽ Moretz, star of Kick Ass and Let Me In, has said "Katniss is my homegirl", in a recent interview with MTV, and "I would absolutely die to be in The Hunger Games." Meanwhile, Twilight actress Jodelle Ferland (she plays young vampire Bree) has tweeted photos of herself dressed up as the Hunger Games character for Halloween, sparking rumours that it's an early bid for the part.
The only problem with the series is its level of violence. While it might not be too hard to read about, it's difficult to imagine the sort of things that happen in The Hunger Games being shown on screen and still receiving the expected PG-13 rating. Are there going to be a lot of camera cutaways at crucial moments? Or are we going to see a watered-down version with none of the book's revolutionary political fervour?
Another potential teen movie franchise that was plagued by these sorts of issues was the Northern Lights trilogy, written by Philip Pullman. While the fantasy books were full of moral ambiguity and contained moments of genuine horror, the movie of the first book, The Golden Compass, was sanitised, and many of the plot's complexities were glossed over. Despite the big budget, starry cast and Christmas release date, the film bombed at the box office and plans for two sequels were put on hold indefinitely.
The producers of The Hunger Games could learn a few lessons from those problems (Golden Compass director Chris Weitz vowed that any potential sequel should be "much less compromising"), as they could from the mixed success of the Narnia films, another contender for filling the post-Potter void. While the first Narnia film, The Lion, the Witch and the Wardrobe, made it into the top 35 highest-grossing films, the franchise was dropped by Disney after the sequel, Prince Caspian, barely recouped its budget. The third instalment of the Narnia series was released in November by 20th Century Fox, and has been doing even worse than Caspian: it's not yet certain whether the remaining four Narnia books will be adapted for the big screen.
What made Twilight and Harry Potter a surer bet than the Northern Lights and Narnia adaptations is the ravenous intensity of their fans, combined with the relative simplicity of the stories. The Chronicles of Narnia books might be found on many bookshelves, but fans of the series don't seem to have the same quivering obsessiveness with which Twilight aficionados awaited the first on-screen depiction of their idol, Edward. Hunger Games fans, while less likely to make T-shirts saying "Team Gale" and "Team Peeta" have a similar intensity: just take a look at all The Hunger Games "trailers" on YouTube, painstakingly spliced together using clips from other movies.
Meanwhile, Scott Westerfeld's Uglies series, about a future world in which all 16-year-olds are forced to go through plastic surgery in order to conform to a universal standard of prettiness, has also been optioned by 20th Century Fox, and while the production hasn't yet got the green light, it looks promising. It's a lot gloomier than most teen fiction - although there's a love story, naturally, to sweeten the pill - but its story of peer pressure, conformity and insecurities should appeal to teenagers everywhere.
There's lots more dystopian fiction for teens begging to be adapted - James Dashner's The Maze Runner, about teenage boys trapped in a labyrinth, and The Knife of Never Letting Go by Patrick Ness, about an extreme version of the Information Age, for example - and there are plenty of other sources for film ideas.
The Marvel comic-book series Runaways, about a group of mismatched teenagers who discover that their parents are supervillains and run away to fight crime, has been called "The Breakfast Club with superheroes" and it looks like it's finally being developed into a film by Marvel studios. With lots of wisecracking, action sequences, romance, and delicate handling of issues, it's sure to be a hit, albeit with a slightly more savvy crowd than the ones sighing over Harry and Edward.
Whichever of these actually makes it to cinema screens first would do well to learn from other people's mistakes: first, you don't need a huge budget or over-the-top effects - Twilight was made for just $37m, a fraction of the nine-figure budgets of The Lion, the Witch and the Wardrobe and The Golden Compass. Second, take care when casting your heartthrobs: the perfect blend of brooding yet lovable is a tricky one. And third, stay true to the story and the intentions of the original.