If space is the final frontier, where will "Star Wars" and "Star Trek" fans go after their sci-fi worlds have ended?

Wait a minute, fans say. Who said anything about ending? These worlds go on without end.

The release of "Star Wars: Episode III - Revenge of the Sith" doesn’t close the world George Lucas created in 1977, they say. It just forces them to get creative on their own.

And though the recent cancellation of "Enterprise" on UPN means there’ll be no "Trek" on TV for the first time in almost two decades, people don’t seem to be turning their phasers into plowshares.

So what’s a geek to do?

"The end of ’Star Wars’ means hunting for that new thing," says Adam Fulrath, 33, of Manhattan.

"And it’s out there. We just don’t know what it is yet."

"In the late ’80s, after the first trilogy, we always wanted more because there was so little that filled the ’Star Wars’ void," says Fulrath. "Now, we know there’s more coming, but we’re not sure when."

Like a lot of fans, Karen Grenke, 29, of Brooklyn pins her hope on a TV series Lucas has promised - looking at the early years of Luke and Han - and the prospect of another animated "Clone Wars" series, though both may be a long way away.

"It’s too much! I need sci-fi therapy," says Grenke, a "Star Wars" fan "since forever."

"I’ve always been drawn to space stuff, and that’s completely influenced by ’Star Wars.’ My whole life, I’ve always said, ’Anything that takes place in space - that’s fine, I’ll watch that!’

"But now we’re in a bad moment, when everything’s falling away."

Still, the most committed fans, the sci-fi convention-goers, are happy to wait in the limbo of the time-space continuum.

"My first convention was in the early ’90s, and for ’Star Wars’ fans, anticipation of new movies was always there," says Nikki Watson, 33, of Manhattan. "Part of the fun recently has been the buildup between movies."

Watson says that she looks forward to new stories about her favorite characters - or, when the going gets tough, writing some herself.

"If I feel like I’m missing it too much, there’s always forums on the Internet," says Watson. "And whenever there’s a void I’m feeling, I can escape into the world of my own imagination and create something of my own based on ’Star Wars,’ ’Star Trek,’ or whatever I’m in the mood for."

The end of "Star Trek," on the other hand, is giving fans a chance to breathe after the disappointing fifth series in the franchise, "Enterprise."

"I will continue to be a Trekker," says Sheryl Franklin, a fan from Philadelphia. "There will be new books, there are conventions, and there’s the ’Star Trek Las Vegas’ attraction.

"And when there’s news about a new movie, we’ll get the official word."

Steve Lorenzo, 39, from Queens, says that seeing the old films in new formats will keep him occupied.

"Knowing Lucas, there’ll be multiple DVDs of the movies with different editions and versions to look forward to," he says. "And it’s been mentioned that [he’ll make] a 3-D release of the entire ’Star Wars’ saga, so we’ll be able to see them in a new context."

And while fans note that TV shows like "Battlestar Galactica" and movies like this fall’s "Serenity" (a big-screen continuation of "Firefly," Joss Whedon’s Western-in-space TV series) may fill the void temporarily, nothing moves them like their favorite space operas.

Collecting, of course, will continue to attract a huge part of "Star Wars" fans’ energy and enthusiasm.

"That’s where my personal interest is," says Justin Scioli, 16, of Jersey City, who estimates he owns more than $10,000 worth of collectibles. "The films are ending, but there’s still so much more.

"Even though we’ll miss Lucas’ films, now it’s up to us to carry the torch and carry our feelings into the future," Scioli says.

"This is a huge milestone in the saga, but at the same time, it’s not an end - it’s a new beginning."

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Sci-fi pics: Is future past?

Since it first hit big in the 1950s, science fiction - and the Hollywood movies made from it - has focused on space as a wellspring of ideas and perhaps the salvation of the human race.

But have the stars burned themselves out?

"Both ’Star Trek’ and ’Star Wars’ have done an enormous amount of good in terms of getting sci-fi into the mainstream," says Paul Levinson, former president of the Sci-Fi Writers of America Association.

"There is something unique and irresistible about stories and movies that look out into space.

"It’s the closest most of us will come to the cosmos," he says. "That’s irreplaceable."

Since "Star Wars" opened in 1977 - and "Star Trek: The Motion Picture" in 1979 - other space movies haven’t gone nova at the box office (anyone watch "Battle Beyond the Stars" or "Krull" lately?).

"It does seem like the death of the future, with these two milestones in the genre coming to an end at the same time," says Mark Altman, publisher of the sci-fi magazine Cinemafantastique and writer of the movie "Free Enterprise."

"But I’m hopeful about the upcoming movie ’Serenity,’ which, like the TV series it’s from - ’Firefly,’ is a western in the sci-fi mold. That’s a great combo, and it has the potential be the next big thing."

Above all else, the pulpy nature of sci-fi can’t be forgotten, says Altman.

"What we need is a show about how the world transcends problems to achieve greatness among the stars," he says.

"The original ’Star Trek’ was about friendship, family, camaraderie and," he adds with a chuckle, "finding gorgeous women on every planet."