The middle class in future America will become fractured. The lower middle class will become the lower class because their jobs & skill set will be deemed outmoded as their jobs will be either downsized, phased out, sent overseas, &/or worse yet, automated by machines/robots. Not only the lower middle class will become the future poor, the solidly middle class will experience a similar fate. The solidly middle class will have their jobs downsized. Those who elect to upgrade their education & skill set will have decent jobs. Many in the solidly middle class don't have a strong education nor skill base so they have to upgrade their education & skill set to become more relevant in the 21st century & beyond. Those who elect not to upgrade their education nor skill set will sink deeper into the lower classes.
The upper middle class who have the most education & skill set will have jobs commensurate w/their education & skill set. This is the sector of the middle class who are specialized regarding education & skill set. Their jobs aren't about to be phased out in the current future. Many of the upper middle class who possess more specialized education & skill sets will become part of the upper class.
In summation, the lower middle class will become the new poor because they have insufficient education & skill sets. The solidly middle class have a little more education & skill sets; however, many of their jobs will be downsized or phased out. If they want to stay afloat, they must upgrade their education & skill sets or they will, like their lower middle class brethren, will sink into poverty. The only middle class who will thrive in the 21st century are the upper middle class who possess highly specialized skills & education.