Last time Bethesda pulled this stunt, we got Fallout 4. Whether it's actually a new Fallout is another matter. I'm guessing we're more likely to see a Switch port, probably Fallout 3 and maybe Fallout: New Vegas to go with it. But that's just a guess at this stage.
But let's throw the field wild open. Let's say it could be anything. For today's Big Question, what would you want Bethesda to announce?