The motor bikes are probably not a fun draw for adults, but when we were kids it looked much more appealing. Adults have access to cars, and other transportation: kids don't. As a kid i always wanted a mini bike, and yeah they were fun. After maturing some a small motorcycle did just fine.

These things will never take the place of the fun we have with bicycles though, about the only thing that may take off will be a really good electrical assist for those who commute or those just wanting some extra speed in the wind as they peddle.