A Federal Register notice was issued late today, 12/13/2019, that the 15% tariffs on List 4B are suspended until further notice and will not go into effect on December 15, 2019. Furthermore, the USTR will issue a notice detailing the reduction of the rate of additional tariffs on List 4A products "in the near future".
The Federal Register will published details officially on 12/18 but an unpublished version is downloadable here.