Well, it's not going to end as long as the movies are making money. Since the start of 2014 to now (so including Batman v. Superman), there have been 11 superhero movies released in theaters (including the last Ninja Turtles movie & Big Hero 6). Only one of those (Fantastic 4) has failed to earn at least 180 million dollars at the domestic box office. Fantastic 4 was considered one of the biggest flops in recent memory at 56 million, and it made more than 4 of the past 7 best picture winners and tied with a 5th.
More often than not, these movies make a lot of money, which is why the studios put them out. The studios often know they aren't good (Sony with Spider-Man, Fox with Fantastic 4) but they make them so that they can keep the rights to the characters, and make money off of them. Spider-Man is now back to Marvel, but the deal with Sony still allows them to make a lot of money off the character.
The fact is when Marvel hit it big with Iron Man in 2008, and they made it clear they had these characters and were putting them in this connected universe, the other studios either had to do the same thing, or get left in the dust money wise. So the market becomes saturated, and "normal" movie viewers get sick of it. I'm a fan of superheros/comic books, so I'm going to see them all, even in cases where I know the movie will suck (Fantastic 4, Amazing Spider-Man 2), but because the average viewer is inundated with these kinds of movies, they get sick of them. It's the same with your Twilight/Hunger Games thing, they have success, movie studios think "Oh, we have to make a bunch of these movies" and you get ones that aren't quality, but they make money because teenage girls will go see them.
However, most prognosticators believe that it's more of a "when" as opposed to "if" this bubble will burst. You can look at westerns, sci-fi, whatever, but these things go in cycles. Something will be big for a while, then the studios make too many of them, people get sick of them, they move to the next thing. You see stuff return and become popular again, but that's how it goes. As long as these movies keep making money for the powers that be, they will be a mainstay in the theater.
TL;DR version: The studios want money, superhero movies make money, at least for now. As long as they keep making money, we keep seeing Batman/Superman/Spider-Man/The Avengers.
