Fable 3 will support Project Natal in some fashion. The confirmation came during a lecture at BAFTA in London. The news was confirmed by Eurogamer's Johnny Minkley, who tweeted the info during the event itself. Molyneux also reportedly showed off Milo and proved that Natal is capable of scanning objects (people, presumably) in bad lighting.
Molyneux himself hinted at the possible inclusion of Natal in Fable 3 as recently as two weeks ago, though he neglected to confirm it for fear of a quick, sniper-borne death.
So that's that then: Fable 3 will use Project Natal. Of course, we don't speak for everyone, but we can't wait to pretend to fart in front of a crowd of adoring, virtual townsfolk.