"X-Men: Days of Future Past" is about to be shown next month while "Avengers: Age of Ultron" is already filming. Both films already have sequels following them, but what happens after that?

Superhero movies are at the top of their game now, and they're expected to lord over the box-office for the next 3 years at least. However, other genres like YA films are also making their mark, and there is a possibility that the market might get saturated.

Fox has always been open to the possibility of a crossover with Marvel. Among the four studios, they are the only ones who have yet to create a sure superhero hit to break $500 million. Even Warner's "Man Of Steel" reached $800 million.

Marvel is solid at the top already with two billion dollar films and consistently breaking $600 million with every release ("Captain America: The Winter Soldier" is on course to exceed that). It is not in their best interest to make a crossover as yet.

But the possibility continues to be teased, specifically on a plot point of view. Director of "Days of Future Past" Bryan Singer talked with Entertainment Weekly:

"You won't feel at the end of the movie that it set up Apocalypse. What it does is it sets up possibilities. But what we'll discover in Apocalypse is that events in this movie made that happen. Apocalypse deals with ancient mutancy. What would humans have thought mutants were? What would mutants think humans were? You're dealing with gods and things like that. And what if one survived and what if that found its way into our world?"

Allusions to gods and the inevitable clash with the human world seem invite one to read between the lines and surmise a reference to the Avengers.

Singer continues: "[The 'Apocalypse' movie] won't necessarily create an alternate universe [like the comic], but there may be some swapping things that I'm playing with.

Simon Kinberg, one their writers, adds: "From a visual standpoint it actually may be a bigger movie than Days of Future Past because there'll be disaster movie imagery, like the title would imply."

The scope of "Apocalypse" may really be an apocalypse of sorts, and the non-mutant heroes, foremost of which is the Avengers may have something to say about it.

Someday, the four rival studios-or at least the three Marvel comics stakeholders would find the need to bind together to ensure the domination of the genre. No doubt, if ever that happens, Fox and Marvel will be the first to collaborate.