EDIT - There's a new Fallout:
It doesn't seem like there's any information out there right now, other than that it's in Vault 76 (is that anything significant? I don't know my Fallout lore). Find out more at E3, I guess.
Vault 76 was a Virginian area Control Vault (IE that's no outrageous Vault Tec testing, just take people, get them in the vault, and reopen after X years or if given the Vault Tec All Clear Signal, spoiler alert, that signal never sends). It's set a mere 25 years after the Bombs fell, meaning it's a fresh, Post-Great War Virginia set in a time BEFORE the BoS even took down the Supermutant Master's Army, before the NCR, before the Enclave conflicts, before the rise of the Minutemen and reveal of the Institute. For Context: Fallout 1 is set in 2161, a whole 59 years AFTER the events of this game.
This is going to be about Vault 76 attempting to reclaim and rebuild the United States in a brand new world. One of fresh mutant animals, Supermutants, ghouls, and an absence of law.
Because it's set so soon after the Great War, it's a Vault numbered 76, which was also unveiled on 2076, 300s after the founding of the United States, it's likely we may a see the Enclave make an appearance, and maybe even in a more positive viewpoint this time around.