A fourth movie has been confirmed by Fox. I'm too lazy to find a link, but I have seen it somewhere. The title "The Last Stand" only means this trilogy is over. Any further movies will go off on seperate story arcs, involving different characters, but hopefully still containing some of the same cast.

From what I've heard, the Magneto movie will follow his past in WWII and him trying to get revenge on Nazis. I would hope this story would show his meeting with Charles, and maybe even some of Wolverine's story from the war. If I remember right, Wolverine and Captain America worked together to break Magnus out of his concentration camp, though they didn't know who he was at the time. I'm not sure if this was from the Comics or one of the shows.

For A Wolverine movie, I would love to see something made out of the Origin saga. I'll let anyone who doesn't know that story discover it on there own, as I'm getting tired of typing...