It looks like 20th Century Fox is attempting to create their own over saturation of Marvel films!
20th Century Fox, who currently hold the rights to X-Men and Fantastic Four films, have taken up half-dozen dates between now and 2021, and confirmed that they are planning to release as-yet-undisclosed Fox/Marvel collaborations on those dates.
The Exhibitor Relations Twitter page reports that Fox has now marked June 7, 2019; November 22, 2019; March 13, 2020; June 26, 2020; October 2, 2020; and March 5, 2021 as release dates for what will almost certainly be comic book related films. Now the films may mostly X-Men films along with related spinoffs, there are reports that Fox is considering once again to create an all-ages Fantastic Four.
The most recent upcoming releases include New Mutants is and is set to be released in theaters on April 13, 2018 followed by Deadpool 2 will follow that up on June 1.