Odds of Hanging On
Once you've sold a few pieces of your own work, or once you've secured a job as a one-size-fits-all glass molder, shaper, or caster, you can generally hold on and have a decent career. Demand for glasswork is slow but steady (source).
The real question is whether you can maintain the career for the long term. In a factory, as long as you maintain good work you'll be fine. If you're self-employed and there are no benefits, then you better be making some real cash. It's not the best gig if you're concerned about retirement.