Looks like Bethesda Softworks and Zenimax Game Studios are in development of an online version of The Elder Scrolls Series (for both PC and Mac). Which they plan to release sometime in 2013.
The things that has been revealed so far, is that the game takes place a thousand years before the events in Skyrim. And that the player can choose from three different fractions. More info is most likely going to be released at the E3 event in early June.
GameInformerSweClockers (Swedish site/forum)