Ah, Tamriel, the epic, sprawling continent in which all of The Elder Scrolls has taken place. Cyrodiil is home to the center of the empire (and Elder Scrolls IV: Oblivion), Morrowind's land is half continental and half island (and was seen in Elder Scrolls III: Morrowind), Skyrim is the snowy, northern location (and, obviously, contained The Elder Scrolls V: Skyrim), and Hammerfell is mostly desert (and was featured in The Elder Scrolls II: Daggerfall). With the MMO, we want to explore it all seamlessly.
Seriously, look at that world map, it looks like the perfect MMO world already. We want all of it. Not "some" or "most" - all. There are also just enough locations that haven't been explored so that die-hard players will be greeted with something new around every bend.