Wrath of the Lich King has been announced as the second World of Warcraft expansion pack by blizzard this week, The trailer (totally unimpressive and un imaginative) is availible here.
Blizzard lists the following as new features:

• Master the necromantic powers of the Death Knight - World of Warcraft’s first Hero class.
• Quest to level 80, gaining potent new abilities and talents along the way.
• Learn the craft of spell augmentation with the new Inscription profession.
• Brave the harsh new continent of Northrend, the icy domain of the Lich King.
• Engage in epic siege warfare, deploying mighty siege engines to lay waste to destructible buildings in your path.
• Transform your hero’s look with new character-customization options, including new hairstyles and dances.
• Explore perilous new dungeons filled with some of the deadliest creatures — and greatest treasures — on Azeroth.
• And much, much more…

No comment from me at this point, the game has way too many problems without adding another expansion