Could the 5.7 earthquake in Utah be a precursor to a larger one?
Short answer: Yes, but the odds are small.

The USGS page that you linked to also links to a forecast: "According to our forecast, over the next 1 Week there is a 1 % chance of one or more aftershocks that are larger than magnitude 5.7." 

USGS also notes:


  No one can predict the exact time or place of any earthquake,
  including aftershocks. Our earthquake forecasts give us an
  understanding of the chances of having more earthquakes within a given
  time period in the affected area. We calculate this earthquake
  forecast using a statistical analysis based on past earthquakes.