As it turned out, Microsoft tried to make a new game in the Fallout franchise without the help of Bethesda Game Studios.
According to insider Jeff Gerstmann, this project was handled by one of the internal Xbox Game Studios.
Jeff did not reveal any details of the new Fallout. It is assumed that this project (most likely) has already been canceled:
A Fallout project was being developed in another studio owned by Microsoft, but, as I understand it, it most likely will not see the light of day. As for remakes: I don’t think [Bethesda] itself will do them. I think they will be outsourced. For example, the same Fallout 3 remake, I believe, will be entrusted to an external studio. However, I think that new games will continue to be developed by the same key people [from Bethesda], and they will probably still have quite serious control over the franchise.