(Mild spoiler ahead.)
Adapting the comic book story arc for Days of Future Past is one thing but it now seems like director Bryan Singer has also watched the 90s X-Men animated series and taken a nod from that as well. In the animated series, Bishop is the time traveler and is sent back to prevent Mystique from assassinating Senator Kelly.
In X-Men Days of Future Past, Wolverine has the time traveler role but it now seems like Mystique may have the same role she had in the animated series. According to Singer in an exclusive with Total Film:
"Raven [Mystique] herself is more militant in this movie. She’s discovered things and she’s on a very singular mission of vengeance. But her very simple mission of vengeance is unfortunately one of those rocks that plunges into the river of time that creates the most devastating of ripples. So with her it’s about whether she’s going to become the assassin character we see in the first X-Men movies, or whether things can go another way."
Even though Singer doesn't clearly say it, it can now be implied that Wolverine is sent back in time to prevent Mystique from completing an assassination attempt. X-Men Days of Future Past releases in theaters on May 23, 2014.
To read the entire Total Film exclusive with Singer, click right here to go there.