Bethesda has released a teaser video of the upcoming Fallout 76. We do know that the new game will be 4x larger than Fallout 4.
Gameplay specifics are not yet known. There will be a single player campaign but the game is designed to be played coop with some friends.
In the teaser there are hardly any NPC in the game outside the players themselves. There are several hostile creatures which suggests the game is trying to be more of a classical shooter.
The game has some nuclear strike areas where players can search for launch codes. This gives the player the ability to use the weapons.
Stay tuned for more as it becomes available.