As far as I an recall, with the exception of Fred (and Harmony briefly) none of the old L A gang have shown up, or, as far as I can recall, even been mentioned since Dark Horse took over the "Angel" title. It's never been mentioned, but, in my imagination, I've always thought that Gunn, haunted by what he became and how he acted in the "After The Fall" arc, either killed himself or followed the examples of Bruce Wayne, Oz, and, now, Dr Strange, and wound up in a Tibetan monastery. He may show up again, somewhere, as a costumed superhero, maybe with Connor as his sidekick.
Uh, Gunn totally appeared in season 9 of 'Angel & Faith'. In a small role, yeah, but still. And he's human now, of course.
I think that season 11 of 'Angel' is gonna end with Angel going back to L.A, and reuniting with whoever's left of the original gang, including Gunn (which, in retrospect, is what season 10 of 'Angel & Faith' should have done, IMO).
Also, am I the only one who thought that season 9 planted the seeds of a possible Gunn/Faith romance? Faith seemed awfully happy to see him...
My memory of that first Season of "Angel," is somewhat sketchy, but I think that Gunn was a vampire in hell during IDW's "After The Fall" arc, but Angel tricked the Senior Partners into sending everyone back to a time before he was turned, therefore making him human again.
Gunn/Fred is Frunn, Gunn/Faith is Funn. Problem solved.
But yeah, Gunn is happily fighting the fight back in LA as of A&F S9, he tells Angel that Nina got married and a couple of other things. For this more settled down version of Gunn I think him and Anne Steele are a nice fit; him helping out at her shelter during 'Not Fade Away' was a very sweet moment.