The premise of the article is flawed - it's not about where the old programmers have gone, but whether they were there to begin with.

If you think a bit about it it's fairly obvious. Programming is a relatively new profession that has been booming for the last decade or two. 30 years ago when a 45 year old programmer would have thought about what to do with his life programming would only be an option for the few. Theresimply weren't that many people that chose a profession as programmers, so naturally there aren't that many old programmers around since there weren't that ,any to begin with.