Update: Zenimax Online Studios have updated the blog post, basically reverting their statement. The Elder Scrolls Online will work like any other game on PS4 and Xbox One - if you have the disc you can play it. And so you will be able to rent, borrow or buy the game used without any problems.
Original story:
ZeniMax Online Studios decided to clarify a situation that was apparently confusing some players, involving the console version of the game. As this is an MMORPG, where you need to be online to play at all times, players will actually be buying a license to play, not the disc with the game. This means that if you buy a used copy The Elder Scrolls Online, and the license has already been used, you will not be able to play it and you'll presumably have to buy a license to do so (essentially buying the game twice).
You can install the full game and download the updates, but you will eventually be blocked when attempting to log in. This is by no means surprising, but it is worth warning console gamers less accustomed to such policies. In other words, you won't be able to buy this game used, rent it or borrow it from a friend.