Ad Hoc in Yountville
Last weekend, after dinner at TFL, I asked Corey Lee about it, and he said that it will be a temp restaurant lasting about 8 months, or until the concept for the permanent restaurant is finalized. He didn't say for certain, but I gathered that the leading concept at the moment is for a casual burger joint. The three chefs (Keller, Lee, and Cerciello of Bouchon) will alternate creating the single $45 fixed daily menu (a la Chez Panisse). They will not be taking reservations.
Not sure how much of that is repeated from the SF Chronicle article, but I'm tired and too lazy to look it up. Hope it helps.