The phrase "sign of things to come" is often used to indicate that a particular event or occurrence is a harbinger of what is to come in the future. There are many synonyms for this phrase, including "omen," "portent," "harbinger," "indicator," and "foreshadowing." Each of these words can be used to convey a sense of anticipation, excitement, and sometimes even foreboding about what is to come. Whether you are discussing the arrival of a new product, a political change, or a major shift in societal norms, using any of these synonyms can help you capture the attention of your audience and create a sense of suspense and intrigue.