I still can't play Skyrim on my toaster and it is 2017. Please make Skyrim Legendary Toasted edition and only then start working on Elder Scrolls 6 ...
In all seriousness though, they can only milk their back catalog so much. It is getting to the point where they will either have to reveal Elder Scrolls 6 at e3 2018 or earlier, or they will have to give us a new ip. What else can they put out at this point?
You have Wolfenstein 2 and Evil Within 2 this year. It is too soon for a sequel to Doom 2016 or a Dishonored 3, and it is way too soon for a new Fallout. Prey didn't sell well enough to make them rush into a sequel so... Elder Scrolls 6 or big new ip for 2018 seems inevitable to me.
They aren't stupid. They know what fans want and they really have no option but to listen if they want to stay in business, but why rush out Elder Scrolls 6 when you can squeeze every penny out of a 6 year old game first?