The Ford Fiesta ST was the best thing Ford cold have done for the Ford Fiesta model. The ST model was an instant hit so when Ford mention that they were going to expand their RS lineup, the fans automatically assume that the Ford Fiesta RS was going to be one of the models.
However, much to the disappointment of the fans, the Ford Fiesta will not be one of the models that will be getting the RS badge. Ford made it clear that the Ford Fiesta ST was going to be the fastest Fiesta we will be getting.
That is why it hurts to look at the concept created by artist X-Tomi here. The artist came out with a rendering to show us what the Fiesta RS would look like if Ford decides to offer it. The design is created based on the Ford Focus RS model.
Looking at the rendering, it does feel like the Fiesta was made to wear the RS badge sadly, we will never see it on the road.