The synthetics are going to get scary - even now, for example, people are dying jades to make them look older. In 2100, there'll be a parade of limited-edition Barbie dolls, Beanie Babies, and Star Wars memorabilia, and none of it will be worth anything. I think objects from the California crafts movement of the 1950s and '60s. That movement redefined the pot from a functional object to a sculptural object. They really started a movement, and those crafts are undervalued and overlooked.
Contemporary glass is the same thing.
Some of these contemporary craft people have redefined the medium. Today, when contemporary art seems to be more about video art, these crafts will probably gain value. In the furniture area, George Nakashima and the Memphis movement will probably be valuable in 2100. Impeachment documents will be big. That blue dress from the Gap will be very valuable.