In today's Hollywood, studios claim release dates as early as possible and then chase that date by trying to get a film out in time. Sometimes this is a bad thing because things can get rushed, but other times, and if scheduled far enough in advance, there is usually more than enough time for a movie to be made and hopefully be good.
Fox has one true release date attached to an actual movie title right now and that's for their next Wolverine movie, LOGAN, which is due out on March 3, 2017. Besides LOGAN, the studio doesn't have any titles attached to any of their set release dates.
Meanwhile, the studio's only real guarantee right now is most definitely DEADPOOL 2. Outside of this sequel, they seem to have a new possible new mutant team property with writer / director Josh Boone's NEW MUTANTS coming soon. Also, rumored to be in some stage of development are DEADPOOL 3, X-FORCE, GAMBIT and a possible X-MEN ensemble film which could be a soft reboot of the franchise.
Fox lost one of its previously saved dates for a Marvel movie on October 6, 2017 which is now taken over by KINGSMAN: THE GOLDEN CIRCLE. However, the studio has claimed November 2, 2018 and February 14, 2019 for future untitled Marvel movies.
So as of right now, the following is Fox's Marvel movie release schedule:
March 3, 2017 -- LOGAN
March 2, 2018 -- Untitled Marvel movie (Probably DEADPOOL 2.)
June 29, 2018 -- Untitled Marvel movie (Maybe NEW MUTANTS?)
November 2, 2018 -- Untitled Marvel movie (A GAMBIT gamble?)
February 14, 2019 -- Untitled Marvel movie (Possibly DEADPOOL 3?)
Those are just our quick guesses as to what movies could be attached to these dates.