The next big thing
is not so much a thing
as it is an idea
The next big thing is something that every company has wet dreams about. It is the ephemeral, ideal thing that every consumer will want as soon as they hear about it.
Consumers, of course, have no real control over what the next big thing will be. The marketroids and media determine it by telling the average joe what they are allowed to like.
eg: backstreet boys, and their clones