The traditional American family with its breadwinner husband, homemaker wife and 2.5 children is rapidly becoming extinct, according to feminist Betty Friedan and futurists Isaac Asimov and Alvin Toffler.

Families of the future will commonly come in multiple forms, including single-parent families, two-paycheck couples and intergenerational communes, they told a sometimes-cheering audience of 2,000 Monday at a National Assembly on the Future of the Family in New York.

"If we do not choose to destroy ourselves by cheering on the person in charge of The Button," said science-faction dean Asimov, "we will be living in a world more different from our world today, than our world is different from George Washington's."

Sophisticated computers, advanced communications systems, new architectural structures and revised job schedules, the trio predicts, will help all family members work together as an egalitarian team.

"We aren't witnessing the breakup of the family," Toffler said, "but a revolution in the structure of the family."

Sponsored by the National Organization for Women's Legal Defense and Education Fund, the day-long assembly featured more than 60 specialists in government, business, social service, education and labor addressing a broad range of issues on the family.

"We want to develop innovative and practical solutions to family problems of the 1980s," said NOW-LDEF president Muriel Fox. "We plan to articulate an agenda for the next decade. Some of the thinking that will emerge we hope will result in new legislation."

The "number-one problem," for the family of the future is child care, she said.

"Fifty-seven percent of women now work and by 1990, 75 percent will," noted Friedan, who said even now just 7 percent of American families meet the traditional concept of husband at work, wife at home, two children.

"In the future, most women won't have the economic luxury of being full-time housewives.

"At the end of the United Nations' Year of the Child, we're spending less on child-care program than we were 10 years ago. We're the only nation that does not have serious child care. It's an idea whose time has long since come."

The family assembly marks "a historic turning of the corner for the women's movement," Friedan said in a luncheon speech with Toffler and Asimov on families of the future.

"The first stage was confrontation. We're ready for the next stage of innovation, restructuring the institutions of work and home."

Although Friedan cautioned that the fight for equal rights for women is not over and won't be assured until passage of the Equal Rights Amendment, she said equality "won't be achieved in terms of women alone . . . we've got to make equal rights liveable, to be able to choose to have children.

"Twenty years ago we began the women's movement, breaking the barriers of society that defined women solely in terms of childbearing.Sometimes this was seen as women against men or, in the strictest terms, women against the family.

"Today it is clear that the very changes resulting from the drive to confront our own personhood brought us to a new stage with new problems. So it's time for the next great leap . . . helping families deal productively with the enormous opportunities and problems resulting from freeing women, men and children from old sex-sterotyping roles.

"We're confronting women's own need to love and be loved, nurture and be nurtured in our new priority for the family. There is a family mystique we are going to break through, just as we broke through the feminine mystique." (Friedan authored in 1963 the book, "Feminine Mystique," from which many people feel the women's movement sprang.)

Many women have traded the role of baby-maker for the role of superwoman who does it all, Friedan said. "That's not the answer," she said to resounding cheers. "We don't want to change frustrations of housewives for heart attacks.

"As we're told how to dress for success or how to succeed in a man's world, I hear women saying 'What is it doing to me? I don't want to be like those gray men in the executive suits with their heart attacks and ulcers.'

"And I hear young men asking this question, too. I see men struggling with their identity, not so much threatened by the women's movement as they are envious. A great many American men no longer think success in the rat race is enough."

What will make equality liveable in the future?

"The economists must give us some concepts that will take into account the work women have always done in the family that will be shared by men, women and children in the future," Friedan said.

"The architects must give us some housing to meet the needs of the families as we are today . . . all the different ways we are living together to meet the needs of mutual caring and support.

"We'll need different kinds of services and appliances that don't depend on full-time housewives. We'll need more flexitime and changes in the hours of work.

"Men will be able to share nurturing and be self-caring in a way they couldn't before."

Demand for these changes is already evident, she said.

"Executives won't accept transfers any more because families and other things are more important in their lives. Those ('company-man') policies kept men from being full-time partners, made him a bread-winning instrument and made the family weak.

"The new, evolving family, based on the equality of women, will be a stronger family, better able to resist dehumanizing aspects of the corporate framework. Then we'll move closer to human liberation."

Alvin Toffler, whose 1970 book "Future Shock" described the disorientation caused by too much change, too quickly, credited the women's movement with helping to launch a new societal revolution.

"When I talk about a revolution," he said, "I don't mean charging the Winter Palace with bayonets.But when I see role structures cracking and reforming, I know I'm in the presence of a real revolution."

Toffler calls it "The Third Wave," the subject of a forthcoming book.

"Our 300-year-old industrial civilization is in ultimate crisis," he said. "We are moving to a new wave of social and technological innovation. The restructuring of institutions is what is beginning to take place."

Comparing the third wave's impact to that of the agricultural revolution and the industrial revolution, he said, "The industrial society was a mass society, and the nature of that society demanded conformity and unity.

"Mass communication, mass production and mass distribution had as a societal standard the single-family.

"The second-wave society is now being shattered. When I look about today I see people living outside that framework. The nuclear family model was appropriate to factory production and an ecologically wasteful society.

"We're moving to a new diversity of energy forms, technologies. The family of the future will not be a single family, but take on multiple family forms -- single-parent, community living.

"I look at the variety of family forms as positive, not negative. When I hear presidents and popes talking about a return to the family, they're talking about a second-wave family that's now obsolete."

Advanced technologies will shift some work back to the home, Toffler predicted, easing the energy crunch and aiding family interaction. "A substantial slice of the population will work in their 'electronic cottage.'"

Said Asimov: "The computer and communications systems of the future will alter our world without recognition.We won't have to gather in factories or beehives.

"Communication will be such that we can have the information we need at home if we wish it, or meet with five people on five different continents."

If we don't destroy the earth through overpopulation, said Asimov -- whose latest book, "A Choice of Catastrophies," outlines ways the world could end -- children will be valued more.

"I'm looking forward to a future with a lower birth-rate society," he said. "Whenever there is less of something, it becomes more valuable. When a woman bears a child it will be a public treasure.

"No one will ask 'Can we educate that child at public expense?' because it will belong to all of us and because the world isn't safe without an educated public, particularly with technological advancement."

A self-described "people-ist" who considers feminism the "best way to do it at the moment," Asimov foresees a "more unisex society."

"Women will be able to do things as easily as a man even if she has a child, particularly if the child is a national treasure. We are fighting in the direction of the wave of the future.

"And the people who are going to lose out are the people who try to prevent it. They will be drowned in the tidal wave."