One of the problems here is how the stats at ‘end game’ plateau so quickly. In other MMORPG’s, the end-game is to further your stats for character progression.
In GW2, the stats are so equal at the highest level that any new item with even slightly higher stats would be considered overpowered – due to this, until the new expansion pack comes out and ‘mudflation’ allows us more powerful items, the only way GW2 can dangle the carrot in front of us is to provide us with new skins.
However, it seems to me that they haven’t considered (or maybe they have) that any new skins on weapons would turn peoples attention away from the legendary skins as they switch their focus to something that could be more achievable. The only answer to this would be to make those unique skins almost as difficult to obtain as the legendaries themselves.
Afterall, who would put themselves through the effort of crafting a legendary bow when you could get a unique one much easier?