Here's the thing, I have legendaries that I love and know that eventually they'll be obsolete, Fatebringer is an excellent example. But I expect that there will be new legendaries coming that will take their place i.E. Word of Crota, Black Hammer for Praedyth's Revenge, etc. This is something I've come to expect from playing other MMOs like WoW, where expansions come out and new gear replaces old. If Bungie decided to update old gear with new stats they might have to do that with the armor as well. Depending on how you look at it this could be a good or bad thing. Personally, I'd say bad, because it would lower my drive to replay a newer raid to get the newer gear and weapons. I understand that this will vary by person though.