The General Social Survey, conducted every 2 years, measures public opinion on a wide range of moral issues. The data from the 2020 survey are expected to be released in mid-October 2021. In advance of this data release, we make predictions for how public opinion will have shifted since 2018. We also predict further public opinion shifts for the coming decade up until the year 2030. These predictions are based on the theory that an opinion will become more popular over time if it holds an argument advantage, that is, if it is better justified by generally accepted kinds of arguments than the opposite opinion is. While this theory has successfully accounted for historical opinion trends, this is the first time it is used to predict future shifts. To assess the accuracy of our forecast we will compare it with the benchmark forecast that predicts the same public opinion in 2020 as in 2018.