Oh, so she just happened to be an Asian chick with purple hair and a red tattoo over her eye but meant to be cast as someone else? Gee, who could she have been? Maggot?
The second time I saw X3 confirmed for me that she was totally off-camera when her two homies got disintegrated. I don't believe that was a coincidence either. It was probably done just to stir up the fanboy controversy we're having right now.
Truth is, Psylocke is neither dead nor alive, but in creative limbo with Toad, Sabretooth, Lady Deathstrike & Cyclops. All of whom have a small window of oppurtunity to return should the writers decide it.
All they need is a couple of lines of dialogue to explain her return in a sequel.
Wolverine: Wait a sec, I recognize you. You were part of the Brotherhood's attack on Alcatraz!
*Psylocke morphs into a shadow, slips into the floor and and reassembles herself in a different part of the room*
Psylocke: And I escaped THAT little debacle by the skin of my teeth as it were.