Jennifer Lawrence as Mystique in X-Men: Days of Future Past; Image source:

Twenty-First Century Fox (NASDAQ:FOX) knows the superhero movie genre is one of the keys to winning at the box office. Recent reports suggest the company is rebooting its League of Extraordinary Gentlemen property, and mid-May saw the announcement of an X-Men spin-off, New Mutants.

Fox is doubling down on film and content creation and looking to better utilize its properties to make up for some shaky results in its networks segment, and along with big properties like Avatar and unfolding franchises like Planet of the Apes, superhero movies will be big performance drivers. Yet while the company is expanding its stable of comic-based films, its core superhero franchise may be in trouble. Key stars of the mainline X-Men series have indicated that they will soon be leaving the property, and Fox could lose some hard-won ground.

X-Men's future exes
Last summer's X-Men: Days of Future Past was a big win for Fox. The picture not only grossed nearly $750 million at the box office, the highest unadjusted total in the series, but was also a major hit with fans and critics alike. Movies in the series had delivered uneven critical and commercial performance following 2006's X-Men: The Last Stand, and Future Past successfully elevated the series to new heights.

But now key series players Hugh Jackman and Jennifer Lawrence have made it clear that they intend to depart from the X-franchise. Jackman's plan to leave the series is especially troubling for Fox, as his Wolverine character has been in every single X-Men picture to date and played a central role in all but one of them.

Casting is crucial to the success of superhero blockbusters, with Robert Downey Jr.'s performance as Tony Stark often credited as one of the main reasons for the extraordinary success of Disney's Marvel Cinematic Universe. Downey's importance to the Marvel movies reportedly netted the actor at least $50 million for the first Avengers film and $40 million plus points on the upcoming Captain America: Civil War. For additional context on just how valuable his screen presence is to Disney and Marvel, at roughly $75 million, Robert Downey Jr.'s 2014 income would make him one of the highest-paid CEOs in the world, were he a real executive rather than an actor portraying one. Star power matters, and Hugh Jackman is the Robert Downey Jr. of the X-Men film universe.

Hugh Jackman as Wolverine in X-Men: Days of Future Past; Image source:

Jennifer Lawrence's stated intention to leave the series is also a big blow to Fox. Around the time of Days of Future Past's release, Fox seemed giddy about the prospect of stand-alone films starring the actress. Lawrence is one of the hottest names in Hollywood, and her ongoing involvement in the series could have made Fox a major contender to deliver the first hit female superhero movie.

Both actors are slated to appear in 2016's X-Men: Apocalypse, and Jackman is signed on for one more Wolverine solo film, but their impending exits from the franchise represent a significant risk to one of Fox's most valuable properties. For the core movies, the studio seems to be readying Channing Tatum -- who will appear as Gambit in X-Men: Apocalypse and a solo film based on the character -- as the new leading talent of the X-Men films.

The B-Teams
Fox's other big superhero movie property, Fantastic Four, is due to receive a reboot this summer, and the stakes are heightened because of potential pitfalls facing the X-Men franchise. The company's last attempt to endear audiences to Marvel's First Family fizzled after the soggy critical and commercial performance of 2007's Fantastic Four: Rise of the Silver Surfer, but Fox has to keep developing films based on the property or the rights will revert back to Disney.

While there's still more than a month to the release of this summer's Fantastic Four, there doesn't seem to be much hype for the film, which has an estimated production budget of $170 million. Reports of a troubled production may also point to quality issues, which could hinder performance. A poor reception for the movie would make additional reboots even more challenging and could leave Fox with a potentially valuable property that winds up being more trouble than it's worth.

With looming superstar vacancies in the mainline X-Men series and Fantastic Four coming up on a potential make-or-break release, Fox is smart to diversify its superhero projects, even if the payoff of these projects is uncertain. The company's 2016 X-Men spinoff Deadpool is being built with an R-rating in mind, which could significantly limit its audience and put profitability out of reach if the film's budget gets too big. League of Extraordinary Gentlemen presents the opportunity to reassemble some of literature's greatest characters on the silver screen, but the last film was a major flop, and there's been little clamor for a reboot or sequel. New Mutants has plenty of promise, but it remains to be seen how the movie's presumed "young-adult" direction will land with audiences and fit in along the broader X-Men property.

X-Men is still Fox's best shot for keeping up with Disney and Time Warner
Fox has done a lot to build and rebuild its place in the superhero race, and plenty of potential remains with the X-Men license in particular, but its key series seems to be reaching a fork in the road. The franchise provides an excellent foundation for the type of expanded film universe recognized in Disney's Avengers series, but it's hard to imagine that the property will get stronger with the departure of central talent.