Bethesda is working on a "World of Warcraft type MMO", according to legal papers submitted in a court case between the company and Interplay.
Apparently development on the MMO has been ongoing since 2006 and involves "close to a hundred people" and a budget of "tens of millions of dollars".
The game's identity is unknown, but strongly rumoured to be an Elder Scrolls MMO. VG247 has been "reliably" informed of this, apparently, and been told the reveal was supposed to happen last year.
From Bethesda's portfolio, there are two obvious candidates for MMO treatment: Fallout and Elder Scrolls. Bethesda cannot, for the moment, legally produce a Fallout MMO, as Interplay owns those rights.
Bethesda seeks to end that in the current court case, and terminate Interplay's Fallout IP licensing deal that was signed in 2004. It's been an ongoing spat.
That leaves Elder Scrolls. Supporting that assumption are comments made by Bethesda that the Elder Scrolls series will continue as well as Bethesda registering the elderscrollsonline.com domain.
In 2007, Bethesda's parent company ZeniMax hired Mythic Entertainment co-founder Matt Firor to lead development of an MMO. His experience on Dark Ages of Camelot, a traditional fantasy game, closely fits the Elder Scrolls bill.