Problems still arise for X-Men: First Class as the actress playing Emma Frost has already been replaced. Details are scarce and it could be something as simple as Alice Eve getting a better offer elsewhere. I doubt many people will consider boycotting the upcoming X-Men franchise reboot based on the actress playing the White Queen.
There seem to be a lot of inconsistent stories regarding the cast of the new X-Men movie. Reboots are always a risky venture and for every Star Trek there are a hundred failures. The X-Men pose an even greater risk to Marvel because a) it's one of their highest profile creations and b) the X-Men movie franchise is still relatively fresh in the minds of many people.
Of course, January Jones has the required sexy factor for the role as any Mad Men fan can tell you. Matthew Vaughn is still the director of the movie ... for now.