With help from friend-of-the-site Norbert, I have updated the Determining the Age of a Canon Lens
page. It now appears possible to determine the age of a Canon lens based on the new 10-digit serial number.
I say "appears" as this chart is somewhat of a work in process. The numbers seem to be holding out well (or are at most 1 month behind) for the lenses we've checked to date. We can use your help in testing the chart - Please send us any certain discrepancies you find.