I don't think I would put Fugazi in the "absolutely never gonna happen" category. I remember reading a quote from Ian MacKaye a while ago where he mentioned that a lot of festivals had offered them a lot of money to end their haitus for a one time show. The way he phrased it, I remember thinking that it was less "boo we hate festivals and corporations and profit and DIY for life!!!", and more- if and when they play together again its not going to be about who offers them the most money.
Probably still won't happen, but if they did decide to play a one-off (or two-off) show at some point, I can see the argument for doing it at a festival so you can reach as many fans as possible. Maybe that would be GV's angle.