According to Nerd Reactor on Dec. 2, the main reason that Wolverine, played by Hugh Jackman, was picked over the Kitty Pryde in "X-Men: Days of Future Past" for the mission of time travel was because of the character's popularity. For those familiar with the comic book story arc by the same name, Kitty Pryde was the one who traveled through time. In this case, screenwriter Simon Kinberg enlightens the motive as to the reason.
“We made the decision for a lot of reasons, some of them obvious and some of them more nuanced, to make it Wolverine who goes back in time. One reason is that he’s the protagonist of the franchise, and probably the most beloved character to a mass audience".
This could be comparable to "The Avengers" where the characters were given equal screen time in that film, regardless of Iron Man's popularity. In this case, Wolverine takes center stage.
"Probably the bigger reason is that when we started thinking about the logistical realities of Kitty’s consciousness being sent back in time, to her younger self, as opposed to her physical body being sent back..it was impossible. Obviously in the book it’s Kitty..but you’re talking about an actress (Ellen Page) who, in the age of Michael Fassbender and James McAvoy, would have been negative 20 years old. So we started thinking again, and the first reflex response to that was a character who doesn’t age. Wolverine is the only character who would looks the same in 1973 as he does in the future".
As seen in the end tease of "The Wolverine", the audience saw that Hugh Jackman is confronted by both Magneto and Professor Xavier about a paramount situation as a Trask Industries commercial plays at an airport terminal.
When the trailer for "X-Men: Days of Future Past" was released, both Xavier and Magneto give Logan an idea of what kind of personalities he'll be dealing with when he encounters their younger selves in the past. Xavier asked that he be patient. Of course, Logan rebukes this characteristic as a flaw in his personality being that he's always been rather hot headed.
Bryan Singer's "X-Men: Days of Future Past" is scheduled to be released on May 23, 2014.