I don't think there's too many characters yet, I trust Singer to cater to each character and to give them their due.
An interesting question though is who will be the leader of the various teams that the film has. There are three teams one in the future and two in the past.
We can safely say Magneto will be the leader of his brotherhood but who will lead the X-Men in the future and more importantly the past? I don't see Xavier leading the team the way he did in First Class.
Brotherhood
Magneto (leader)
Mystique (2nd)
Booboo stewart (if he plays 70's mutant villain)
Omar Sy (if he plays 70's mutant villain)
any other new characters
Future X-Men
Storm (leader ????)
Magneto (2nd)
Wolverine
Kitty Pryde
Rogue
Iceman
Colossus
Blink
Omar Sy (if he's playing Bishop)
Booboo stewart (if he plays future mutant)
Professor Charles Xavier (mentor)
First Class X-Men
Beast (leader ????)
Havok (2nd, If he comes back)
Banshee (If he comes back)
Booboo Stewart (If he plays 70's mutant hero)
Omar Sy (if he play's 70's mutant hero)
any other new characters.
I wonder who Singer will choose as leader for the Future X-Men and the FC team. Will he follow on from X3 and keep Storm a sthe leader (he did say he isn't ignoring any xmen movie) or will he make Magneto leader? or maybe wolverine?
And for the first class team will he go for beast or will he go for havok. It's a shame darwin is still dead he was the only character to display any sort of leadership qualities in First Class.