The Elder Scrolls Online is doing just about the most exciting thing it can: a Morrowind expansion.
It's due 6th June on all platforms and introduces: a new zone, Vvardenfell, and a 30-hour story; a new player class, the Warden, and his War Bear pet; and a new 4v4v4 PvP arena mode, Battlegrounds.
Vvardenfell is apparently the same size as in The Elder Scrolls 3: Morrowind - occupies "the same geographic footprint" according to the press release. All the landmarks from TES3: Morrowind should be there, albeit set 700 years earlier.
You'll be able to jump straight into the Morrowind content as a new player, bypassing all the existing Elder Scrolls Online stuff. Doing it this way costs Ł40/€60, which includes the Morrowind expansion and base ESO game. If you just want to upgrade, it's Ł30/€40. There are fancier editions and pre-order bonuses available too.
With no subscription to pay, it's a big push by Bethesda to pull people to Elder Scrolls Online with a new kind of Morrowind game - particularly on PS4 and Xbox One where no Morrowind experience is available. If those players stick around, the whole world - which has changed a lot, and for the better since launch, obviously - will benefit.