hopefully it's just optional co-op... i don't think they'd force you to play online, perhaps it's a drop in drop out kind of online...
in another "leak" they said the settlement building was an experiment for fallout 4 to see if they could make this 76 game work... and since settlements were largely a success, they went ahead with 76...
this same "leak" also said they're gonna mention something about TES6 at E3, soooo ...
i think it will be quite interesting to play a game 25 years after the great war... yes, no supermutants, but there's still deathclaws and ghouls... i'm just imagining the vault dwellers emerging from the vault and seeing a similar scene outside of vault 101 with dead skeletons wanting in... and when they walk out to cheerfully proclaim they're here to rebuild the world, a gang of raiders starts firing on them ...