Why would there be any doubt that a PSP feature would carry forward? Well, for one thing, between the PSP version and now, Skype was purchased by Sony's competitor Microsoft; for another, the PSP Go proved that we can't expect any feature to carry forward from one Sony handheld to another, not even playing PSP games.
When it acquired Skype, Microsoft said it planned to continue supporting versions on non-Microsoft platforms, so it's not impossible that it would continue supporting Sony handhelds. Right now, this is unconfirmed, as neither Microsoft or Sony offered comment when queried by Joystiq.
Sony PlayStation Portable PSP-2000