The follow-up takes it name from the classic 1981 Marvel comics story by Chris Claremont and John Byrne that depicts a timeline created by the X-Men’s failure to prevent the Brotherhood of Evil Mutants from assassinating a U.S. senator. In that alternate future, the giant robotic Sentinels have become the de facto rulers of the United States, where mutants are hunted down and placed in internment camps. How much the movie will borrow from that seminal storyline is unclear, but Fox's new Marvel creative consultant Mark Millar teased just last month that "Days of Future Past" is "'X-Men' meets 'The Terminator.' You’ve got robots, you’ve got time travel, you’ve got superheroes -- it’s got everything in one film.”
Although "X-Men: First Class" director Matthew Vaughn had signed on for the sequel, he abruptly withdrew from the project in October, to be quickly replaced by producer Singer. Of course, Singer also directed Stewart and McKellen in 2000's "X-Men" and 2003's "X2."
Stewart's return to the franchise doesn't come as a complete surprise, as he let slip in September that there's "every possibility" he would be playing Professor Xavier again.
"X-Men: Days of Future Past" opens July 18, 2014.