I've read online in a few articles from back in the the summer that Lionhead already have plans for Fable 3,4 & 5 which is great news considering it's become my favourite Xbox series.
There is a video interview with Peter Molyneux on the 360 dashboard where he, from the way I understood it, basically gave away a large part of the series story.
He mentioned...
Theresa. He said that no one seems to have "got it" that there is something about Theresa. He asked "Why has she been alive for 500 years?" and mentioned her final line in the quest "Leave the spire now. It's mine." and he asked "What's she going to do with that?" which, to me, basically tells us that a large twist is going to be Theresa was the villain all along and used the Hero to gain the spire and get on with her plans.