On March 23, 2018, President Trump signed into law the Omnibus Spending Bill to fund the federal government, which contains provisions to renew the Generalized System of Preferences (GSP) until December 31, 2020.
U.S. Customs and Border Protection (CBP) will apply GSP retroactively to entries filed after December 31, 2017, provided a request is filed with CBP within 180 days after the bill is enacted, and contains enough information for CBP to locate or reconstruct the entry.
The renewal of the GSP will go into effect 30 days after the House passed the legislation.
The text of the Bill may be found here:
https://www.congress.gov/bill/115th-congress/house-bill/1625/text