Bryan Singer is expected to do two more X-Sequels, the first one aimed at a 2002 release.
Tom Rothman, a 20th Century Fox exec, told the Hollywood Reporter the following. "We're going to try…good news about it is -- you don't always do it, but in this case we had planned should we be fortunate enough to have success we're in a situation where all the principal actors in the film are signed for sequels. And the good news, also, about the X-Men universe, itself, is that there are many other characters. So it lends itself to a series because there's a lot of very interesting material over the 20-30 years of the underlying material. So we're certainly going to try (to do a sequel).We'll see where this movie goes. But, we're going to try."
Also, Singer told USA Today that "We don't want it to get too cluttered in the sequel, but look for a grand finale finish with many characters in the third installment."
Thanks to Wes for his help.