Speaking as a fan of the Fable series, I think this is a good thing (and certainly not the doom & gloom that a lot of people seem to think it is).
I've no interest in rail-shooters or Kinnect games, but I'm glad that Lionhead have fulfilled their desire (or commitment forced upon them by Microsoft) to make a Kinnect controlled Fable game by making a separate, spin-off prequel (judging by Theresa's apperance, it's set between Fable and Fable 2), rather than by shoehorning Kinnect into Fable 4 (or even Fable 3 as it was once rumoured).
Fable: The Journey isn't Fable 4, much in the same was Fable: Pub Games wasn't Fable 2. It's just a separate project set in the same universe that utilised Kinnect so requires a totally different game style.
Halo Wars wasn't the end of FPS Halo games, GTA: Chinatown Wars won't stop GTA V being made, and Fable: The Journey won't prevent a more traditional Fable 4 from existing.