In a Comic-Con video interview with Collider, Mark Millar opened up a little about his role with Fox as a creative consultant on their Marvel Comics properties, specifically the X-Men family. As rumors of expansion of the X-Men line fly, with a X-Force movie being written, The Wolverine taking #1 in its opening weekend (albeit with a considerably lower haul than the previous solo Logan movie), and X-Men: Days of Future Past already beginning its media ramp-up 10 months before release, it does certainly seem like Fox wants to do more with the mutant franchise.
"I think there's about five to ten potentially golden franchises," Millar told Collider while noting that at this stage they are only "very vaguely" talking about many possibilities for expansion.
The five to ten number may seem like a lot, or may seem low, depending on how you look at it. Marvel Studios, at the moment, has really only built three core franchises (Iron Man, Thor, Captain America - we're leaving Hulk out as he was recast after one film, with no solo film on the near horizon), with a fourth if you include the team of Avengers as a whole. They are largely treading the same ground with Phase 2, though expanding into potential franchise #5 with Guardians of the Galaxy. That takes them, then, into 2015 when they'll start to really expand with Phase 3. Even if, for some unforseen reason, they made no sequels in Phase 3 save Avengers 3, that's still only a total of say eight potential franchises by the end of their 9th year of producing films in the Avengers family.
Fox, of course, has been doing X-Men films for thirteen years already, but could be starting from relative scratch after the time-bending and reality-re-writing Days of Future Past hits theaters next May. Regardless, they're only currently occupying two of those "five to ten" slots with X-Men and Wolverine. X-Force makes a potential third, and the long in development hell Deadpool brings us to four, with lots of openings thereafter. Would Fox consider a Cable solo movie? Certainly, especially if X-Force works. How about Madrox or X-Factor - either the government superteam incarnation or the mutant detective agency... sure! The fact is, for as many Marvel Heroes as have been Avengers, there are at least as many, if not several more that have served with an X on their costume at one time or another.
Currently, Fox only has Days of Future Past on its release schedule, and hasn't taken a page from Marvel Studios, who announced three film release dates without any hint of title or character, but this quote by Millar could be the first sign of something bigger on the horizon.