Well, I know at least four people who have said they're interested in performing, and that's just among my personal acquaintances. Ideally the first panel (Filking 101) will take place anywhere from hours before to the day before the second one (the performance workshop), so we might have some new folks, too.
(If we have the internet, then I can cue up YouTube karaoke tracks on my laptop and run 'em through the speakers for rudimentary backup for any new, spontaneous at-con filks.)