Ever since Fable III was announced at Gamescom it has been assumed that it would incorporate Project Natal in some way or another. Peter Molyneux did not dare confirm it back then, but at a BAFTA event yesterday he confirmed Fable III would indeed support Project Natal and that it would also include microtransactions.
I'm sure we will get more information on Fable III soon whether Microsoft likes it or not. Peter Molyneux has a tendency to talk about his games whenever he gets half a chance...