William Shawn, the longtime editor of The New Yorker, has promoted two associate editors to co-managing editors. Shawn said that the two may eventually succeed him and serve as co-editors of the magazine, but that he has no immediate plans to retire.

John B. Bennet, 39, will be managing editor for non-fiction and Charles McGrath, 37, will be managing editor for fiction. Bennet came to the magazine in 1975 and McGrath in 1973.

"It's just a way of strengthening the organization for the future," Shawn said yesterday, "and that's about it. The details still have to be worked out."

For years the literary world has delighted in speculating about what will happen to the magazine when the 77-year-old Shawn retires, but this announcement provided the first solid clue to Shawn's plans. Editor of The New Yorker for 32 years, Shawn wields final control over its content, approving every word and cartoon, and both insiders and outsiders have said it is difficult to imagine the publication without him. He is only the second editor in the magazine's 59-year history, succeeding founding editor Harold Ross in 1952.

"There hasn't been any really clear picture of what was going to happen before," said author John McPhee, who has been published in the magazine for 20 years. "There have been lots of rumors, but there wasn't any specific announcement like this. I'm very pleased about it. I think it's a sign that some definite and sensible action has been taken."

Shawn told the staff of his decision last Thursday, and made it public in an interview with The New York Times published Monday.

"The morale of the staff is better for it," said staff writer Burton Bernstein, who has been at the magazine for 27 years. "We feel that if Shawn should retire, we won't be rudderless."

Shawn served as a managing editor of the magazine from 1939 to 1952. McGrath was, however, careful to explain yesterday that he and Bennet may never follow Shawn's path.

"That's a big if," he said. "Shawn has said that's simply a possibility among many."

The magazine, which has a circulation of 480,000, has no masthead, and even within the offices there's a certain deliberate vagueness about job descriptions. The internal staff list, McPhee said, consists only of names and phone numbers with no titles. The absence of obvious hierarchy has fueled the speculation over the years.

"I guess people here learn not to pay attention to it," said McGrath, "because it's so often wrong."

And now that the speculators have something concrete to mull over, people within the magazine are insisting nothing monumental has happened.

"I don't get the feeling that there are going to be any great changes immediately," said writer and editor Roger Angell, a 29-year veteran of the magazine. "Things don't change quickly here."

McPhee aggreed.

"It's not a great, big, huge change," he said. "It's just a sign that a progression for the future is being built in more than a vague way. The editor of the magazine this morning is the same one who was the editor the last thousand mornings."

The New Yorker, with its consistency in its top editors, has little experience with transition. As Angell said, "We don't know how to do this."

The magazine has changed over the years, he said, but "it's changed by the writers. It's not changed by plan. People don't say, 'This is how we want to go.' The writers and artists do with their work. I don't think anyone can say where we'll be in 10 years. It's not on the drawing board anywhere."