Bethesda's 2017 E3 showcase could very well close out with The Evil Within or Wolfenstein, or maybe even Fallout VR, but I think we might see a glimpse of something new.
After last year's E3, Bethesda revealed that it has two new games in development that are on the same scale as Fallout, and neither is The Elder Scrolls VI. Todd Howard did confirm that a follow-up to Skyrim was in development, but it was a long, long ways off -- implying it may not even be this console generation!
So that leaves us with the two brand new games of which we know nothing about. We don't know how long either of these games has been in development, although Howard did say (in the same article linked above) that both titles would be announced before The Elder Scrolls VI. That leaves us to assume that we could see one of these new titles revealed this year. A new IP would be the perfect way to close the conference, even if it is just a trailer.