IGN recently caught up with Singer who is out promoting his web series "H+" and in asking him about the sequel, the producer of the upcoming film dropped the nugget that it will be called "Days Of Future Past." Again, this isn't surprising with reports back in June suggesting it would be based on that storyline, and more recent updates revealing Fox had already gone ahead and registed domain names under that title. And Singer confirms that it will use that comic run as well as other elements to build the story -- and considering it's based on a two-issue story arc from 1981, that makes sense. Here's synopsis from Wikipedia:
The storyline alternates between present day, in which the X-Men fight Mystique's Brotherhood of Evil Mutants, and a future timeline caused by the X-Men's failure to prevent the Brotherhood from assassinating Senator Robert Kelly. In this future universe, Sentinels rule the United States, and mutants live in internment camps. The present-day X-Men are forewarned of the possible future by a future version of their teammate Kitty Pryde, whose mind traveled back in time and possessed her younger self to warn the X-Men. She succeeds in her mission and returns to the future, but despite her success, the future timeline still exists as an alternative timeline rather than as the actual future. (The Official Handbook to the Marvel Universe: Alternate Universes 2005 gave the numerical designation of "Days of Future Past" Earth as Earth-811).
Singer says the film will be "ambitious" and given the alternate timelines and mind-traveling, he's not kidding. But perhaps more interesting is his suggestion that this time out, they will be using some Marvel-style "connectivity" between pictures in the X-Men universe. And that jibes with stuff we've been hearing as well, and though we can't say too much, if it pans out to what we've been told from our sources, comic fans are going to be really pleased.
"X-Men: Days Of Future Past" will hit theaters on July 18, 2014.