Blizzard on World of Warcraft forums explained that the new jobs were opened for development of new multiplayer massive online game that has nothing to do with World of Warcraft.
This has confirmed rumors that Blizzard is working on a new game on it but nothing is known except that it will be "next-gen MMO" whatever that means.
Blizzard has anyway opened competition for jobs for 3D character and lead 3D environment artists. If you are interested, visit Blizzards official site site.