The horrendous use of "2morrow" might be a clue and not just Internet-speak. Besides, there was plenty of room left in that 140 character-limited tweet. With Mass Effect ready to move on to number 3, that leaves Dragon Age ready for number 2.
Further backing up a major announcement, though completely speculation on my part at this time, is the fact that Game Informer is scheduled to reveal a cover tomorrow.
Shacknews will update you on both BioWare's announcement and Game Informer's cover tomorrow. Who knows, maybe we'll only have to write one story.