Fallout 4

After a week of Skyrim I find myself thinking about Fallout 4. Bethesda used the engine from Elder Scrolls 4: Oblivion to create Fallout 3 (later used by Obsidian to create Fallout: New Vegas). So it seems highly likely that the new engine built for Elder Scrolls 5: Skyrim will be used to create Fallout 4 at some point. In fact I wouldn't be at all surprised if they've already been working on it for a while. There have been no official announcements yet but I'd put money on it being revealed at one of the major gaming events in 2012 (E3 being the most obvious choice). I wonder where it will be set, time to leave the continental US maybe?