20-Year Prospect
How many keys do you carry? You probably have at least one for your car and one for your house, if not a couple more. This is pretty standard, too—we all use keys in our daily lives to enter, exit, lock, and unlock all kinds of things we care about (including diaries). And so long as we have locks, we're going to need locksmiths to save the day when we inevitably lose our keys. In other words, this job isn't going anywhere.
But what about cars slowly moving away from physical keys and toward fingerprint and electronic security? And how about modern buildings fitted with the latest in locking technology?
Sure, the way some locks look and operate might change, but it is incredibly unlikely metal keys will be completely eliminated or replaced by fancier, Bluetooth-based devices. We've been using keys for so long, and they work so well, that it doesn't make a lot of sense to ditch them.
Plus, no matter how much technology may change how we protect our belongings, one thing that won't change is our knack for locking ourselves into/out of places.