If you want to know what will be popular a few decades from now, you don't have to engage in expensive or time-consuming market research. Just look at what rich people have, and think about a way to make something similar, although at a much lower cost, for the average consumer.
For example, in the next 20 years I believe there will be automobiles that can operate on auto-pilot. This will give the middle class the benefit of having a chauffeur, but at a fraction of the cost. Think of how great it will be to always be dropped off and picked up where you are going, instead of having to trek to and from some parking lot.
Businesses that provide middle-class people with access to items that previously only the rich could afford are almost always successful. When I look at business plans I ask, does this make people's lives "richer"? If it does, the business has a much higher likelihood of success.