[Source] The writing was all over the wall with hints given in previous chats, and developer ZeniMax Online Studios confirmed the business model for The Elder Scrolls Online today. It is plain, simple monthly subscription, with 30 days of free time for the first purchase.
Quote from the source: We’re building a game with the freedom to play – alone or with your friends – as much as you want. A game with meaningful and consistent content – one packed with hundreds of hours of gameplay that can be experienced right away and one that will be supported with premium customer support.
Charging a flat monthly (or subscription) fee means that we will offer players the game we set out to make, and the one that fans want to play. Going with any other model meant that we would have to make sacrifices and changes we weren’t willing to make.