It doesn't work like that, you can't "bet your career" on a language. Either you are interested in continuous learning or you aren't, and it's pretty clear which one is a better choice when choosing between multiple employee candidates.
It does actually work like that, for me. I'm in my mid thirties and have worked in financial software development for over a decade. Given the day rate I'm earning for Scala development, I will be able to retire comfortably long before Scala goes out of fashion.
Of course, I'll still be coding for fun after I've retired, so I'm looking forward to learning Swift in my spare time, alongside the other languages I code regularly in.
Nice to hear it has worked well for you! I'll then modify my statement a bit a say that I would never suggest "betting a career" on a single programming language, but to of course dive in if a good opportunity presents itself.
