Supererogatory has dug up a job advertisement where Lionhead are looking for people to work on a game using Unreal Engine 4 - Epic's next generation engine.
There's nothing to say what game this may be, but given what Lionhead have been working on since Microsoft bought them - Fable 4 isn't exactly a wild guess. Given that they are wholly owned by Microsoft it is also reasonable to assume this project is only heading towards the next Xbox.