Rian Johnson’s Star Wars: Episode VIII was recently revealed to have a release date of May 26th 2017. However it’s also known that 20th Century Fox’s Fantastic Four reboot would be releasing a week later on June 2nd 2017. In lieu of this information, Fox has now pushed their release date another week further to June 9th, 2017 as to not get caught up in the Star Wars madness.
Fox will now release THE FANTASTIC FOUR 2 on June 9, 2017.
— BoxOffice (@BoxOffice) March 13, 2015
Disney may own Star Wars, but let’s not forget that they also own Marvel Studios. Added to that is the fact that Marvel Studios doesn’t really have a great relationship with 20th Century Fox, especially since they aren’t supporting the Fantastic Four reboot in any way, shape, or form via the comics or outside marketing. I wouldn’t put it past your own guesses, but Disney might be pushing its weight around to protect little brother and make sure that the Fantastic Four comes out as a fantastic flop. We can only guess…
May the Force be with you all. 
Source: BoxOffice