It depends on the concept of the movie, on how Mojo and Arcade would work... Think of it this way, the concept of x-men 4, heres an idea, after the events of M-Day aka the end of x-men 3, a major political debate occured causing the fractions and a devided between how humans view mutants and mutants view humans, feeling isolated and using a giant grant from the goverment, They create "THE ISLAND" a hidden oasis created by the dharma initiative "Joke" created by the goverment as a safe heaven for a mutant community to exist without fear from redicule of humanity. a home they call genosha
However, despite the wonderful mutant offer, there are still those who are willing to start a war, and having all the mutants in one place makes them a bigger target than ever.
The Friends Of Humanity declare an all out war against mutants by using one of the most infulential media's to turn people against mutants. Enter Mojo addams the obbess tv excutive, his aim is to capture the true nature of mutants by creating a documentary show to show how hostile mutants can be. After a prevoked attack by the friends of humanity, Mojo manages to capture Beast although defending himself, in the wrong context looks like he is attacking mutants. So what happens, Iceman has to step up as the new x-men leader to try and amend and uncover the true nature of the friends of humanity with the aid of the x-men. and to stop another war from occuring. But who is arcade and what is Murder world?