First off, I wouldn't consider the 'best ADA programmer ever' a very good programmer if he had only used ADA his entire career. The first thing a good programmer does is start looking at other tools, ie, languages, that may meet their requirements better than their current tool. Good programmers also look to other languages to help expand their knowledge of their current language.
If you don't have experience in a certain language then go get some. Again, a good programmer should able to pick up a new language pretty quickly. When it comes to interviews most of what I have encounter are algorithm based with very few being API quizzes. A list is alway a list and a sort a sort no matter what language you implement it in.
And sure there is some age discrimination out there, but I have friends in the late 40s-50s who have no problem finding jobs. They actually have companies chasing them because they have a proven track record of delivering quality software that solves problems.