http://www.ign.com/articles/2013/08/22/fable-legends-beta-begins-in-2014-no-plans-for-fable-4
Lionhead's multiplayer Xbox One game, Fable Legends, will have a beta in 2014. The developer detailed the plans in its forum, stating, "We will release new and more information about the game on our website, including opportunities for beta testing the game in 2014. Make sure to sign up to be kept in the loop as we will release more information throughout the coming weeks and months."
The post also states that "Fable Legends is the only Fable core game in development, and we have no plans to make a sequel to Fable III." You can expect some familiar Fable elements, such as pub games, customizable skills, moral allegiances, and, indeed, a single-player experience.