The domain name elderscrollsonline.com was registered on 15 August this year by ZeniMax Media Inc, parent company of Bethesda Softworks - the lovely people who make all those wonderful Elder Scrolls games.
Adding fuel to the speculation, ZeniMax Media obtained 15 million US dollars in funding from Providence Equity Partners Inc in late October, which will be used "to fund future growth, increase game development and publishing, facilitate acquisitions, and finance massively multiplayer online games (MMOGs)." [our emphasis]
Bethesda, the Elder Scrolls, and MMO development. These things potentially add up to Massively Tasty Online Games.