Developer Lionhead has posted a survey, asking players to give them feedback on the Fable-series. There are questions about which functions have been the most important in the game, and also which of the three Fable-games was your favorite.
Hopefully all the feedback (the company just tweeted that they have already recieved more results than expected) will help improve Fable IV, which we certainly can expect to arrive at some point. You can read about their thoughts on doing this on Lionhead's site, or simply take the survey yourself.