Dive summary:

• A question that may affect builders' strategies is whether growing families will need more new homes if baby-boomers do not follow the usual practice of down-sizing when kids move out of a house.
• The economic disruption of recent years may have kept some larger homes off the market while owners waited for prices to recover, but will they now decide to sell or to stay put?
• One research group, the Bipartisan Policy Center, expects a glut of larger homes from which growing families can choose over the next 40 years, but Harvard's Joint Center for Housing Studies predicts that only about 15% of boomers' 46 million homes will go on the market between now and 2030.

From the article:

Unfortunately, the crystal ball is cloudy on the answer, since years of economic uncertainty have disrupted the usual practice of moving up while your family is growing, then moving down when they've flown the nest. ...