The “pros” don’t predict the trends, they create the trends. They choose what to do based on past popular trends and the cultural climate at the time, as well as paying attention to the trends in other markets, particularly those in Europe and Asia, as well as popular trends music, movies, television, celebrities, etc. For example, when Walk the Line premiered, there was a slight resurgence in fashions similar to those trends. Consumer reports, surveys, and sales records are good indicators of where things are going too.