A teaser trailer for Halo 4 concluded Microsoft's E3 news conference today. In it, the series' longtime hero, Master Chief, awakens from cryonic sleep to the voice of Cortana, calling him by his name. He then grabs Cortana and flees the wreckage a ship hurtling toward some sort of portal.
Microsoft's Don Mattrick said Halo 4 will be "part of a new trilogy." The game is due for a holiday 2012 release.
UPDATE - You can catch the game's debut trailer right here.