"The family structure will need to change. The nuclear family can't be sustained for much longer by many, many people. Look for a return to multi-generational extended families."
I think you're right on that. The economic cost of starting a household is just too steep for young couples. It makes sense for other reasons as well; in-house care of children and elderly family members, shared values, etc.
Another not so positive trend (and I'm hardly in a position to criticize) is an increasing number of people simply deciding not to have children.
People just assume that it's just a "values issue," but that only takes it so far. It's also a question of making the most efficient use of resources -- personal resources, such as housing, money, time, etc.
Think of how people use the resources in an elevator. They will arrange themselves, without a plan, in a symmetrical fashion to create the most "personal space" in an environment with limited resources. Same holds true for families.