I'll give you a few examples. First one being "This Is the End". Won't be huge at the BO, but it takes enough teenagers (14-20 yo) out of a MOS seat on opening weekend. Small, but it's a dent.
Second would be World War Z. No matter how good MOS ends up being, there are going to be a ton of females dragging their boyfriends into it just to see Brad Pitt. Not to mention the increasing popularity of the entire post-appocolyptic world movie genre.
Third and probably the heaviest hitter will be Monsters University. This movie is going to reel in every single kid in America due to the brilliance of it's first movie. Whenever you're dealing with a superhero movie, you can always count on kids seeing it. However, with Monsters University coming out 4 days later... It's going to take a hit.
Throw in piracy, people being pissed off with the last Superman, the anti-Snyder people... There's more than a couple things going against it.
Reason I changed my mind is because of the advertising. WB did a phenomenal job with the TV spots. The anticipation is growing, quickly.