We should be able to upgrade legendary and/or raid weapons and armor, albeit it at a lower cost than exotics (say 4,000 glimmer and 3-5 ascendant shards or energies - depending on the item). This could be done at the gunsmith and at the character's vanguard class representative (for weapons and armor, respectively). If this isn't done to allow us to keep up with the rising level cap, raid weapons will ultimately become useless in future content, and we will all (eventually) be wearing the same raid armor, albeit with different shaders. Also, I'd really like to be able to upgrade the stranger's rifle. Since I hit 20 it's just been sitting in my vault, waiting for the day it could become useful again...