A few days ago in a video tour given to IGN by Peter Molyneux he said that he was pretty convinced that online co-op was going to be a 1st day patch for Fable 2.
But then, a few days later they said that there is a strong possibility that it will ship with the game like they originally planned. Either way, we won't have to wait long. Besides, I'm waiting til xmas, so it's all good.
Here's the fable 2 thread... http://www.forgehub.com/forum/gaming-discussion/31208-fable-ll-cant-wait-get.html