The FAA has been planning on implementing a change requiring the use of the ICAO Flight Plan Form for filing all domestic flight plans in the United States as of October 1, 2016. Today they issued a notice that the change has been delayed until January 2017. They say that the additional time is needed to allow flight plan providers/processors to test the changes to the system.
They have also provided a list of changes that pilots will see in filling out the ICAO form rather than the U.S. Domestic flight plan currently in use.