We're not going to have humans flipping burgers in a few years. A lot of these low-wage, low-skill jobs are finally on the brink of being automated. There will be new opportunities to replace them, as there always are. I'm pretty optimistic about the future of the economy - we have a huge number of skill-demanding fields that are growing, and many of them are facing real difficulty, which is exactly what creates demand.
How many people will be employed by the companies that replace all these low-wage low-skilled jobs? What will those formerly low-wage low-skilled laborers do after they are replaced? Buy a college education? Learn robotics?
As those jobs are automated, who will patronize those businesses? eg what fraction of McDonalds customers are high-income high-skill laborers vs lower-wage low-skill?
Human cognitive abilities follow a normal distribution. Some low-skilled laborers never had an opportunity to reach their potential, others lack the capacity to perform higher skill jobs... and some people are incapable of even "low-skill" labor.
Is automation maintaining or reducing the number of jobs for less capable people? Are we slowly raising the unemployable-threshold?
Those are good questions. Our challenge becomes ensuring that people are capable. How many of those displaced workers are less capable because of something intrinsic (some mental defect or insufficiency), and how many just need to be trained? I'm not sure if we'll ever reach a point where the "average" person is unemployable, but we can imagine a future where that is the case. But there's such little genetic variation within humanity that it seems likely that our education system could be made much more rigorous and suitable to ensure that everyone comes out of it at a very high level of capability.
But no matter how you slice it, pay is a function of supply and demand. Nothing more, nothing less. Burger flipping is low-wage because everyone is willing to do it, and people will undercut each other to secure that they get the job over someone else. The changing economy may make all jobs more difficult, but there will still be jobs that the masses gravitate to, and those jobs will remain low-wage as a result.
