A Geeky Viewpoint

Two years from now there looks to be an epic Super Hero Battle, Captain America and Batman and Superman as the three legendary heroes collide head on, AT THE BOX OFFICE.
  
Both movies as schedule to be released on the same day, and word from both camps is neither is going to blink.

Warner Bros. president of domestic distribution Dan Fellman "no intention of moving 'Batman' off that date"

"Disney will hang on to the May opening slot for Marvel's movies with Avengers: Age of Ultron and Captain America 3 in 2016"   Bob Iger CEO of Walt Disney.

Clearly on movie needs to move as the competition not only decreases potential ticket sales for each it could major havoc on the individual theaters in sales, including concession sales.  

Who blinks, who moves....   Batman vs Superman almost inevitably.  

Marvel has since 2003 released 8 movies on that weekend with 4 more planned.     They have clearly staked out that weekend and no matter how much Warner Bros. would like to muscle its way in, Batman vs. Superman is currently a light weight in terms of box off sales.  

There is a silver lining for Warner Bros.  April 2016 is pretty devoid of movies and has been proven by Captain America you can be successful at the box office during what has been considered a dead month.