My understanding is that Lionhead was purchased by Microsoft, so my guess is that they also purchased this IP.

As for there being any chance of a Fable 4 coming out? I think that is unlikely. Fable 3 got a lot of hate because the game was rushed and clearly the last 3rd of the game had so many cuts that it was a sad patchwork that made it end abruptly. Plus, Microsoft mishandled Lionhead for ages. . . they were working on a Kinect tech demo/game that allowed you to interact with a little boy AI through the device (Milo & Kate - I think), and that got cancelled, then we didn't hear from them for ages until Fable Legends was announced and yet again we didn't hear or see much of it for ages and now it is cancelled. Basically, they bought the company and rather than fostering it to get good games from them, they drove it into the ground. . . so they aren't good caretakers.

There is an outside chance that another company might try to purchase the IP from Microsoft, but I don't see why you would need to do so. . . it's not like the IP has a highly marketable well-known cast, the series is more of an idea about an open-world game that allows you to simulate the life of an adventurer from childhood into adulthood with all of life's personal decisions as well as those of an adventurer. That's a lovely concept and if you're a spiritual successor, you have more freedom as well as not having to pay for an IP that would have limited marketing appeal, and could, given that you aren't the original owners (hardcore fans will hate you, look at the hardcore who spend their time hating on Fallout 4 (probably despite having over 50 hours played time with it)) of the IP and the fact that Fable 3 was unfinished and the fact that the original was over-hyped hurt your sales more than it helps. I wouldn't buy it. . . not after Microsoft wiped their ass with it.