There's a larger question of whether this workforce can be trained that many times or not. I don't think we have a choice, so I'd rather just go out and fix the problem instead of ruminating over it. We have a very nasty tendency to ruminate and self-flagellate over structural problems instead of just going out and fixing them.
I do know that we can't use the same institutions, programs, and policies that got us into this to get us out, and I know that there is a huge population that is going to resist the necessary change.
(and btw, "fixing the problem" may not involve retraining. Hell, we might end up personally outsourcing each of our lives to several generations of folks in developing countries and picking up a profit on the difference in standards of living over the next 50 years while the average skill level in the world equalizes. Lots of possible solutions, and I'm not sure I would define the problem as simply as an obsolete workforce)