yes, James will play Charles again, that's for sure. the same with Michael, January and Kevin.
I had a thought some days ago..
what if this new trilogy works this way?
Xmen First Class: set in the 60's
Xmen Second Class: in the 70's
Xmen Third Class: in the 80's
This way, the new trilogy would tell all the story of the x-men, since the 60's to the present day, with X3.
It would be interesting, without doubt. If you decide to do a trilogy about the past of the x-men, it should tell all the past of the team, not just their experience in the 60's. Three movies set in the 60's is too much, I think. It would be a big wasted opportunity.