Unlike Sony which had to renew the Spider-Man film rights to make Spider-Man 4, 5, and 6, Marvel set up their agreements with 20th Century Fox so that as long as they keep making movies based on the properties they have the film rights to, the film rights stay with Fox.
The X-Men franchise isn't going to leave Fox anytime soon on account that Wolverine 2 is obviously going to happen along with X-Men 4, Deadpool, and other X-Men side projects looking very likely.
Fox confirmed in an incredibly *****ey manner that they're rebooting Fantastic Four (like a day after the Disney takeover of Marvel was announced) and have Akiva Goldsman (Batman & Robin) on board as a producer and screen writers. However, if things don't get moving, they can still lose the rights after a certain period of time.
They also announced a Daredevil reboot last year but well nothing's happening and the rights are due to expire anytime soon on account that it's been almost 5 years since Elektra. Unless Fox decides to continue being the bane of the Internet Geek Community and just suddenly announce a film to keep the rights.