After a lengthy, and somewhat tedious, wait on Bethesda's Twitch channel, we finally have a name. While we won't find out more for a short while, until Bethesda's E3 Conference on June 10th, Fallout 76 is confirmed. There seems to be a strong possibility that this could refer to the Vault that is based up in Washington D.C. according to Fallout lore which you can read into here.
There's only so much you can pull from a trailer at this early stage, but the 76 on the jumpsuit seems to strongly suggest this. We'll find out more in less than 2 weeks time.