Here is what Matthew Vaughn had to say about the addition of only one major new character in the proposed X-Men: First Class Sequel.
"We will only have one more new character. I won't say who he...I won't say who he or she is! But we will only be bringing one more new character in. Because, I think, as Professor X is in a wheelchair, Magneto needs to have a nemesis he can fight with. Someone that will be his equal. I know who it is. It would be nice if I could say something, but I can't, mate!"
Matthew Vaughn also doesn't rule out the possibility of Sir Ian McKellen and Sir Patrick Stewart showing up in the sequel via a flash-forward.
"I have worked with Sir Ian McKellen before, and he is a lovely guy. I would love to work with him again. So, never say never!"
X-Men: First Class was released June 3rd, 2011 and stars James McAvoy, Laurence Belcher, Michael Fassbender, Bill Milner, Kevin Bacon, Rose Byrne, Jennifer Lawrence, Beth Goddard. The film is directed by Matthew Vaughn.