I'm a little thrown off by how exactly it looks like Fallout 4. Is this their attempt to make a New Vegas release off their own product?
Yet the rumors of an online component persist. Combined with the fact that this is a control vault, apparently releasing humans out into the irradiated wilderness prior to Fallout 1, you're playing what amounts to the people that become the gangs and ghouls. Because of this, I'm thinking maybe it's a small online survival game ala RUST, Ark, Conan, etc. etc. People group up on a server to survive and rebuild, kill monsters, etc. It seems to fit.
My preference would be another single player explorer, of course. But I won't get my hopes too high up.