It's not Hellion. In Uncanny #500, on the top of the page it says, "Epilogue Three: Enter the Pixie." When they go on and on with all their "Oh my god"s about how much they love Dazzler, Pixie says "I swear...coming to San Francisco was the smartest thing I've ever done." Not "we've ever done."
I also just read issue #501 (thanks to Marvel) and there was no mention of who it was. Pretty sure it was just a human friend of hers.
Nah. Basically throughout the issue, when a mutant/X-Man was on panel for the first time, their name was given in a little box along with a little blurb. Nothing was mentioned on this dude. Pretty sure he's just some random guy Pixie knew. I haven't read a whole lot of the New X-Men stuff with him but he just doesn't seem the "oh my god..." type.