Upon the release of the next content patch, the current debuff limit of eight is being increased to sixteen. This should allow players a little more freedom in using abilities which add debuffs, aiding in a number of encounters throughout gameplay.
To my knowledge, the user interface (displaying five debuffs) has not yet changed, but I'll look into it.
http://forums.worldofwarcraft.com/threa ... 306067&P=1
Good News