The core Fable games are solid RPGs, but Microsoft and developer Lionhead Studios had trouble keeping the series' momentum. The franchise took bizarre turns into brawling and first-person spellcasting. Today, the most recent Fable title was cancelled and Lionhead has been closed. That seems like it would be the end for Fable, but don't write it off forever.
Over the weekend, Microsoft's Phil Spencer responded over Twitter to a fan inquiry about the possibility of Fable 4:
@dragen_Light Nothing to announce right now but I do think the IP has a lot of places it could go.
— Phil Spencer (@XboxP3) April 30, 2017
That response certainly stops short of making any promises, but it also doesn't definitively shut down the chance of more Fable in the future.
I hope that when Spencer says "a lot of places it could go," the first thing on that list is "back to being an RPG." Experimenting with ill-fitting styles and genres is what diluted Fable's identity and alienated its fans.