Every update choose 5 raids to to add 1 new piece of loot to to the table. With 4 updates per year, this means that every raid will have 1 new item in it each year.

Seems like an easy way to keep old raids relevant and maintain interest in running them. It was pretty cool a few years ago when items like Thaarak Wraps and Omniscience were added to HOX and VOD, which revitalized those raids for a while.