I think they should have trading but no trading raid gear and no trading the weapons you can only obtain through exotic bounties. Also when you trade it gets reset and they have to earn the upgrades themselves. Also bungie said this- "As for swapping irons in the Tower? Nope. We want you to earn ‘em. You should be able to tell a badass story for every sweet jewel in your arsenal. Once you earn them, the various Guardians under your account will be able to trade them, but weapons belong to the players who acquire them through action and bravery." How is I traded a few strange coins for it from Xur any different than I got it from a buddy or some random guy at the tower.