Usually, Call of Duty games have their single player campaigns revealed long before their multiplayer or zombies modes, but most people are expecting a multiplayer event this time around. (gamingintel.com)
Also, if you're planning to get the retail version of the game, the cart will only have the Single Player campaign (due to size restrictions). (perfectly-nintendo.com)
The difference will be that we'll still have our single player campaigns and you'll just have a pile of dead servers. (blog.us.playstation.com)