Using truth or gally does not make a difference unless you are in a solar burn nightfall or want to solo crota NM (even then you can probably solo crota with truth. 3 rockets will probably do it). If they quit, bungie won't care. They got their money. They aren't going to go through the work of taking gally out of Xur's loot table (doesn't sound like much but remember, we are dealing with lazy bungie here) for no reason dude.