Because you see it comes in the form of an amusement park called 'Bethesdaland' and there's two attractions still under construction and listed as coming soon. The other visible attractions include nods to Quake Champions, The Elder Scrolls, Prey, Dishonored, Fallout, and Doom. And so the rules of internet speculation would have us believe that we can expect to hear about two new games coming from Bethesda at E3 this year.
With one of those most likely to be the next game in the Wolfenstein franchise. With the other being, and this is a wild guess, a Fallout 4 offshoot in the vein of New Vegas.
That's just wishful thinking on my part, but either way here's hoping its one of Bethesda Game Studios upcoming massive 'Fallout-sized' projects.