Time Inc., the largest magazine publisher in the United States, with properties like People, Sports Illustrated and Fortune, is preparing for one of the most pivotal periods in its 91-year history.

Within the next six months, its parent, the media conglomerate Time Warner, hopes to spin off Time Inc. into a separate public company. But if the plan succeeds, Time Inc. will become independent at a difficult moment. Not only do the magazine industry’s fortunes continue to sag, but Time Inc. has also shown signs of instability. It has churned through three chief executives in the last three years, and lost a star editor, its former editor in chief Martha Nelson.

To combat these negative forces, Time Inc. will abandon the traditional separation between its newsroom and business sides, a move that has caused angst among its journalists. Now, the newsroom staffs at Time Inc.’s magazines will report to the business executives. Such a structure, once verboten at journalistic institutions, is seen as necessary to create revenue opportunities and stem the tide of declining subscription and advertising sales.

Overseeing these changes is Joseph A. Ripp, a former longtime Time Warner official who became Time Inc.’s chief executive in September. In an interview, Mr. Ripp said it was refreshing to shake things up. In recent months, he confirmed publicly that there would be additional layoffs in 2014. He has also expressed openness to initiatives, including expanding the company’s television programming and conference businesses.