Odds of Hanging On
In the current economical climate, a career as a machinist isn't exactly going to have you draped in riches. It's likely to make family (and other forms of future) planning a little trickier, limiting where and how you can live. If you're frugal and content to live a somewhat simpler life, you'll have no problem hanging on financially.
It's a little harder to say otherwise, however. Jobs for machinists haven't exactly been growing at anything close to an astounding rate. With the constant, exponential rise in efficient technology, that growth rate won't be climbing anytime soon. Take solace, though: if your niche is a bit more specialized and you're a good worker (we have faith in you, dear Shmooper), you'll probably be able to hang on to your job.
When new technology threatens to make your position obsolete, learn how that machine works—you could be able to get a position maintaining or training others on the new technology.