Tim has an interesting post speculating on “which subjects will be the subject of moral revolutions in the 21st century.”
I think there are three ways to identify possible areas for moral change. First and most obviously, you can look at what’s currently in the process of changing and predict the eventual outcome. For example, we’ll see further gender equality, with the idea (e.g.) that women are the best caretakers of children becoming as unacceptable as the idea that, say, Jews are greedy. (Of course, there’s still room for progress there too.)
Secondly, you can think about where your own morals conflict with those more generally accepted by society. Nationalism is an example here; I truly do not understand why people believe that someone from Texas should have more of a right to go to Cleveland looking for work than someone from Mexico does. I think that as our world becomes more interconnected, national boundaries are going to seem less important and more arbitrary, and we’ll start seeing people from other countries as simply fellow humans.
Third, you can think about where your moral intuitions conflict with one another, or don’t match with reason. Here it’s difficult to predict what will happen, since if you knew how to resolve the contradiction it wouldn’t be a problem, but it provides a way to identify areas of change. Animal rights is a big one here; my moral intuition that stops me from hurting cute things conflicts with my intuition that meat is a normal thing to eat. And it’s not easy to resolve logically. My guess is that meat eating will become less accepted, especially since it’s now easy to get sufficient nutrients otherwise.
I note that my last two examples rely rather heavily on increased prosperity. The more productivity increases, the easier it will be to let more people compete in American labor markets - eventually there will be enough to go around. And technology and prosperity make it easy to survive as a vegetarian. It’s also probably true that increases in material wellbeing make less-economically-fraught changes easier as well; people who aren’t worried that anyone’s going to take their next meal away are more likely to focus on their own problems rather than causing trouble for anybody else. Plus, there are more overindulged college students available for protest duty.