I've heard that this will be the last film in the trilogy, but not necessarily the last X-film. I think that's why they're bringing in characters like Angel, Beast, and Kitty and phasing out characters like Xavier, Magneto, Cyclops, Mystique, and Jean (due to contracts expiring, etc.).
I think Stewart and McKellen would actually be likely to reprise their roles in later films, as would Jackman. Berry, probably not... and probably not Paquin either (sadly).
There is definitely potential for more X-films... the question is whether or not there will be a demand.
