It's been in development since January 2011 by a small dev team, according to leaks. Skyrim's development ending beefed up the Fallout 4 effort. A 37 second trailer was shown to attendees.
The 'War... War never changes...' speech was present. It takes place in Somerville, Cambridge, Arlington and the outlying areas, with Boston its primary focus.
Fallout 4 will be announced before E3 2014 but won't be launching next year, reports, but instead is planned for release around October 2015. Bethesda have no plans for multiplayer but may include some local co-op options. At the end of trailer a Fallout 4 logo appeared above the 5 platforms.
Start munching your gathered salt pile now.