Internet rumor. Take with a huge grain of salt until proven otherwise.
According to The Daily BLAM! 20th Century Fox has apparently begun screening the trailer for X-MEN: FIRST CLASS to small audiences. They have a detailed (almost too detailed) description of a possible trailer which features all of the mutants and gives more insight into the film’s story.
Fox has yet to officially announce when the official trailer will premiere in theaters and online, but we expect that to be very soon.