If you go
here, there's a link two rare
XMFC featurettes, one where the producers, writers etc. talk about the characters, another where they talk about Erik and his relationship with Charles - and that one made my heart all... achy, with how hopeless their situation is. There's a part where all the
X-Men films are summed up, the relationship between Magneto and Professor X, and it's said, paraphrasing now, "They are both so disappointed in each other and they just want the other to come back." ;_;

There was also an interview with Michael Fassbender about the sequel:
link.
I have no idea [when we’ll start filming]. I’m looking forward to working with all those people again. We had a lot of fun. It was a great cast and a great crew. Hopefully, I’ll get in at ground level and start putting some ideas together myself, with James [McAvoy] and, hopefully, (director) Matthew [Vaughn], and we can see what happens next.
I’m really interested to see what happens to Charles (James McAvoy), in the next one, and see how he becomes Professor X ‘cause we got to see Erik turn into Magneto, in the first one. It will be interesting to see who shaves Charles’ head. When he’s drunk one night, the mutants will go in there and shave his head and shave off his eyebrows. Maybe.