It's been confirmed that the sequel to X Men First Class will be X Men: Days of Future Past
Bryan Singer exclusively told IGN that the script is being written now,
adding “It’s going to be very ambitious. It’s called Days of Future Past
and it deals with aspects of that comic but also some very new things
but I don’t want to give any of it away. Matthew Vaughan will be
directing and I’m totally excited about it.”
The Days of Future Past storyline was first
published in 1981 and deals with alternate timelines.
Set in a dystopian future in which Sentinels rule the United States,
the X-Men – along with all mutants – are incarcerated in concentration
camps. The storyline was also loosely used in a two part animated version and you'll find this embedded below.