According to a tweet from Tom Gaulton, a lead engineer at Playground Games, the Fable reboot has been in development for over four years. The dude was just trying to celebrate his four-year anniversary at the developer. Hoping he didn’t get any shit for this.
The Fable reboot was initially revealed in July 2020. This would indicate that the title has been baking for a bit and is well underway, or one would think. Also of note, this tweet is celebrating his four years at the company, so there is a possibility that the game has been in development longer.
The last entry in the franchise was Fable III back in 2014.