UPDATE: Well, that didn't take long. The Hollywood Reporter has learned that Kick-Ass 2 director Jeff Wadlow will write the X-Force script for 20th Century Fox with an eye to direct. X-Men franchise producer Lauren Shuller Donner is also onboard. Original story follows...
There are rumours that a X-Force movie could be made after the release of Bryan Singer's X-Men: Days of Future Past, due for release May 2014.
20th Century Fox recently registered the domain X-ForceMovie.com, as spotted by X-Menfilms (via DigitalSpy). Previous X-Men titles have been discovered in a similar way in the past.
X-Force focuses on a superhero team of mutants led by Cable, Cyclop's son from the future. It has a slightly different, more mature tone than the X-Men.
Possibly lending this additional credence is the fact Mark Millar – Fox's consultant on all its future Marvel projects – has recently spoken about possibility of a X-Force movie.
“You have to remember that Fox grabbed the X-Men back in the ’90s because it was the biggest franchise in the world," said Millar in an interview with CBR. "So X-Force or Cable or Deadpool — all these amazing characters are things we haven’t really gotten to yet. ‘X-Force’ #1 was the second biggest book of all time behind Jim Lee’s ‘X-Men’ #1, so there’s an immediate brand recognition to that stuff and a build in fanbase. You go to any convention in the world, and you’ll see 20 people dressed as Deadpool. In a lot of ways, these are Marvel’s coolest characters, so I want to remind people of that and build on what we already have."
And we know Warpath, a one time member of the X-Force team, will also appear in Days of Future Past. It's likely the domain has been registered in case Fox want to proceed with the project at a later date. It could be spin-off or conceivably even a sequel; either way, production will likely rest upon the success of X-Men: Days of Future Past.