The 9/11 law gives individual citizens the right to sue foreign governments and citizens directly for the results of acts of terrorism. This is a bad idea because such entities and their representatives are unlikely to be able to really know who is at blame for any particular act of terrorism. Also there could be large scale retribution from relatively small-time lawsuits. The U.S. government is only starting to recognize the ramifications of this law.
There have been a number of questions raised following 9-11 and the connection of the attackers to members of the Saudi ruling family. The fact that some of of the 9-11 Commission Report remains classified as it relates to connections between members of the Saudi ruling family and the attackers only continues to stoke those concerns. There is little chance that Congress or the incoming Administration will do anything to forestall the progression of civil suits against Saudi Arabia.
Trump's administration will probably have a different attitude to Saudi Arabia then Obama's. Congress passed the 9/11 bill but Obama vetoed the bill.What Trump will do is anyone's guess as the promises he made in his presidential will not likely be kept. The US will not likely change it's law as Saudi Arabia is a too important ally.
Saudi Arabia does not have that much influence over the United States. They have some say because of oil, but there are ultimately many companies involved in the oil industry, and Saudi Arabia is just one country. The United States politicians will get a great deal of pressure from its citizens to allow the families of 9/11 victims to sue for their damages.