The announcement is coming tomorrow, reports the New York Observer:
"It will be a 50-50 merger of the two companies. The editorial staffs will combine under the editorship of Tina Brown, who will again run a high-profile glossy. Newsweek owner Sidney Harman, 92, and IAC chairman Barry Diller had for weeks disagreed over an operating structure for the hybrid publication. The deal reached today establishes a daily role for Mr. Harman and strong editorial independence for Ms. Brown…For now, Newsweek will be called Newsweek and The Daily Beast will be called The Daily Beast, with some intermingling of the names to come later."
UPDATE: The official announcement.