a harbinger of things to come
Something that is indicative of what will happen or become popular in the future. I think this trend is a harbinger of things to come, but there's no way to know for sure.
harbinger of things to come
and portent of things to come; sign of things to comea sample of the events that are to occur in the future. The first cuts in our budget are a harbinger of things to come. Today's visit from the auditors is a portent of things to come.