Cast members Taylor Lautner (L), Kristen Stewart and Robert Pattinson (R) pose at the premiere of "The Twilight Saga: Eclipse" during the Los Angeles Film Festival at Nokia theatre at L.A. Live in Los Angeles
Cast members Taylor Lautner (L), Kristen Stewart and Robert Pattinson (R) pose at the premiere of "The Twilight Saga: Eclipse" during the Los Angeles Film Festival at Nokia theatre at L.A. Live in Los Angeles June 24, 2010. Reuters

The Twilight Saga might not make it to sunup.

With an aging fan base, sexier and naughtier vampires and werewolves clawing it up on TV and a full year to go before the franchise ends, the four-film version of Stephenie Meyer's pre-teen fave will have a hard time crossing the finish line at the level of, say, the Harry Potter or Star Wars franchises.

Sure, Breaking Dawn -- Part 1, which hits theaters November 18, is the movie Twilight devotees have been waiting for: Edward and Bella finally get married and finally, you know, like, do it.

Even those of us above the age of 13 are curious to see if real-life couple Robert Pattinson and Kristen Stewart have chemistry in the big-screen boudoir, especially after director Bill Condon revealed their sex scenes had to be edited due to Pattinson's excessive thrusting.

Last week, fans lined up as Pattinson, Stewart and Taylor Lautner stuck their hands and feet in cement in front of Grauman's Chinese Theater.

And tracking for the next Twilight film is good, with Breaking Dawn the bestselling movie ticket at Fandango as of late last week, according to the site's Harry Medved.

But nothing R. Patz and K. Stew do in theaters will surpass what the randy vampires on True Blood do weekly on the small screen. And as HBO's Blood has stolen some of Twilight's sex thunder with the older crowd, the CW's Vampire Diaries has given the teen set (oh OK, and some more mature viewers, too) a chance to get their fill of soapy vamp drama on a weekly basis.

Plus, the demographic that created that frenzy has grown up. Except for the Twihards, the initial pre-teen-girl fan base -- we all know this is a largely female phenomenon -- has moved on to other things. It's hard to see them still wearing those Team Edward or Team Jacob tees.

In fact, it's hard to see anyone still wearing those tees.

On the other hand, it wasn't uncommon to hear not just kids but twentysomethings, thirtysomethings -- and older -- of both sexes wax on about the Potter books and movies.

Publisher Hachette Book Group estimated that 1.3 million Breaking Dawn books were sold in the first 24 hours of its release in August 2008, a franchise record.

But even that lofty figure can't compete with the 8.3 million copies of Harry Potter and the Deathly Hallows that were moved on its first day of release back in July 2007.

Then there are the Twilight stars themselves.

There's no question that those same fans will be lining up to see Breaking Dawn -- Part 1.

But there's also little question their heat outside the narrow fan base has cooled.

An attempt to launch Lautner as an action hero in September's Abduction hasn't exactly taken the global box office by storm, with the $35 million movie grossing $76.4 million worldwide. It is probably a break-even proposition at best, once global prints and advertising costs are factored in.

Pattinson's April drama Water for Elephants grossed just over $117 million on a budget of $38 million and was a modest success. But the Fox movie featured two Oscar winners, Reese Witherspoon and Christoph Waltz, as Pattinson's co-stars.

His earlier non-Twilight projects included youth drama Remember Me -- also a modest performer, grossing $56 million on $16 million -- and the lightly regarded Little Ashes, in which he played Salvador Dali.

Stewart's between-Twilight projects -- indie films The Runaways and Welcome to the Rileys -- also failed to draw any real buzz or box-office bucks.

And it was cute, sorta, at first, when Pattinson and Stewart tried to be coy about whether or not their on-camera affair had gone off-screen. But as it became more and more obvious that it had, and they still refused to confirm it, it, and they, became kind of annoying.

Ditto the romantic saga of the Taylors -- Lautner and Swift -- which was irksome pretty much from the beginning.

But even if Breaking Dawn -- Part 1 lives up to Summit Entertainment's earning projections ($611 million, according to a studio report issued earlier this year, down from the $698.5 million grossed by Twilight: Eclipse), what about that last movie, which is still a year away?

After the Edward/Bella wedding and Bella's pregnancy, the level of drama in the storyline takes a nosedive (even by overwrought teen novel standards).

If you've read the books and know how the whole thing turns out, well, you know the rest of the lackluster plot may have viewers wishing they had an Abduction DVD handy.