https://www.pcgamer.com/why-bethesda-announced-the-elder-scrolls-6-at-e3/

One of the biggest "wow" moments at this year's E3 came at the tail end of the Bethesda press event, when it finally, officially confirmed that The Elder Scrolls 6 is in development. It was also tremendously underwhelming, because there was literally nothing to it but a quick flyover of some generic fantasy landscape and a logo, accompanied by a rehash of the Oblivion theme with a Skyrim lead-in. We don't even know which region of Tamriel it will be set in (though we've been speculating a bit). With so little to actually show, the obvious question is, why bother at all?   

"A couple of years ago I talked to Todd [Howard] about clarifying with everybody that TES6 was not going to be our next game, and we had two other big games that we wanted to do first. So we had already put that out there several years ago, but we were very vague on what those other two titles were," Bethesda's vp of marketing Todd Howard said in an interview with FZ.se.