Hello Flavio. It shooould be a reunion of sorts for many of the original board members once word spreads on Bryan's return. I hope you have been well buddy.
At any rate, I'm not going to post my actor/actress choices just yet because I want to think about it. But I will list the characters that I believe should have a presence in the film. This will be based on the set-up from Bryan's first X-Men film as well the need to flesh out some additional mutant relationships:
Professor Xavier
Emma Frost (after seeing Avatar this weekend I would still embrace Bryan's original idea of casting Sigourney Weaver in this role--it's just...unexpected).
Cyclops
Jean Grey
Storm (only because she is referenced in the first X-Men film as being an original student)
Beast
Now, here's where things get kinda sticky. Because of FOX's greed to cast every tom, dick and harry in X3, a number of classic X-Men that should be in this film cannot be.

For example, according to the comic timeline, Angel and Ice-Man are original members of the X-Men, but they wouldn't even be born according to the continuity of this movie franchise's timeline.
And this is where not sticking to the comics can come back and bite you in the ass later. And ironically enough, the decisions to cast Ice-Man, etc. as teens in school under the tutelage of an adult Storm, Charles, Jean and Scott were made by Bryan, so it will be interesting to see how he works around this absence.