If those older workers and others are equally or more skilled than the younger ones implied by your question, smart companies will realize the discrepancy and hire them.
In addition, if older workers know that firms place a "high value on undergraduate-level CS theory," they should probably spend some time learning. . . undergraduate-level CS theory.
You can in fact see this in action in other areas—for example: http://www.economist.com/node/17311877 .