Take this with a grain of salt, but this guy leaked Fallout 76 a few hours before its reveal.
He says that Xbox will announce Forza Horizon 4, Gears of War 5, some Halo game, and Sunset Overdrive 2 at this years E3. And you remember that leak from a couple weeks back where it said that "Yoshi's Flipping Island" was a thing? Apparently that whole leak was accurate.
EDIT: Where I first found out the info
The actual post:
Bethesda is announcing Fallout: Vault 76 : gaming