There's a few black or ethnically ambiguous female X-Men characters that haven't been portrayed across the big screen yet, but MikeFenty's right, Storm is the only
relevant one. Still, she could reprise a role in the next main installment or play a supporting role in their X-Men: Origin film series - which could venture off to bigger things.
Wasn't she actually offered a role in the X-Men: First Class movie, but turned it down because of the LOUD tour or something? I remember hearing something about that and crying. Maybe a young Storm..