What do you mean where are we going to get the people?
Did you not include in your thoughts the millions of illegal aliens let in these past few years? Or the fact that there is still American population growth?
The population growth in the US is barely at the replacement rate. And if the economy “grows” (assuming growing the economy adds jobs) the country will need to add millions of skilled workers. Immigration will help (Illegal immigration doesn’t usually bring in skilled labor.)
With the exiting of the boomers from the workforce, the entire worker supply is going to need to be resupplied from somewhere. Robotics will help. But we will likely be in an employee deficit for a while to come.