TotalFilm revealing some decade settings they've discussed. Vaughn wants to stick with the late 60's. As the first film is set during 1962 and the rest of the decade could be explored. It also makes sense as you can't really age the characters too fast if the actors are expected to return. Singer also mentions visiting the 70's and 80's giving the impression that if successful they are willing to make at least a trilogy.
A trilogy would work best as Cyclops, Jean and Storm have yet to be included in the films. I would also guess that characters like Gambit, Psylocke and other underused X-Men characters could be given solid screen time in future films.
WOULD YOU LIKE TO SEE A FIRST CLASS TRILOGY? WHAT CHARACTERS SHOULD BE IN THE SEQUELS?