Ellen, what I heard is that the Joël Robuchon group had pulled out, and that another tenant was being sought. It's too bad, as I would have enjoyed dining there. I visit either L'Atelier or the Restaurant whenever I'm in Las Vegas.
I had also heard rumors of a new Japanese restaurant, but did not have a name. Thanks for the link. That street address should put them where you mentioned, the former Carpe Diem location.