Fallout 4

Bethesda's Pete Hines said: "The whole reason we went out and acquired the license and that we now own Fallout is that we clearly intended to make more than one." He also added: "This is not something we're going to do once and then go away and never do it again. When that will be or how long that will be God only knows, but we acquired it specifically because we wanted to own it and develop it and work on it like we do with The Elder Scrolls."

Past attempts
Black Isle Studios also planned to make a Fallout 4 after their Fallout 3 project (Van Buren). The Caesar's Legion was to be a prominent faction there. However, even Van Buren was eventually canceled in 2003.