In an effort to reduce the confusion caused by the wide selection of equipment released in Guild Wars 2 throughout the years, ArenaNet has decided to update most of that equipment in the next patch. Once the patch hits, the equipment in question will be updated to include all the attribute combinations a player has available at the time. This is based on the expansions a player has.
Of course, these changes mean players are going to have to spend some time managing equipment. The update will reset their gear and they will need to choose traits for them again. A short rundown on some of the affected gear is available on the Guild Wars 2 site — although it is not a full list.