Just like games such as Runescape, players urn to feel that old nostalgic experience.  Runescape similarly started a petition and Oldschool Runescape was released.  So why not bring back Vanilla Servers.  This would in no way hinder the current servers, but would draw old players, and give players a change.  I believe this would be a huge boost to not only Blizzard Entertainment, but the remaining World of Warcraft community.