I read Days of Future Past—the X-Men two-book-saga by writer Chris Claremont, penciler John Byrne and inker Terry Austin—back when it first came out in the 1980s. Based on the new trailer, it seems that is has some key moments from it. Like when Storm gets killed?
At least, that looks awfully similar to her dead by sharp object in the original comicbook:
Perhaps that's why there were rumors that Halle Berry was off the movie. It seems to be in one scene and then she gets killed.
The Sentinels—the robots created by the United States government to control the mutants—from the future also seem quite different from the Sentinels from 1970s, which we knew already. That seems logical. They look like shape-shifting Terminators.