There is only one way I'd be okay with the Gjallarhorn going away--If this is a one-time thing (Bungie admitting, "oops, we messed a few of the guns up"), and going forward exotics will transfer over from year to year. Maybe I'm a minority with this mindset, but I don't see the point of working hard to collect exotics that won't retain their value after a year. I want my favorite gun(s) to come with me over the next few years. If I don't feel like that's happening, realistically I'll probably quit Destiny, because I won't feel like I'm "building" my character.