Can the new opportunities replace the fading print market and collapsing library sales? Probably not for everyone. However, many of the old rules still apply. Quality and originality still have value. Niche specialisms are always in demand. Surviving as a freelance in the digital age requires new skills and an openness to new markets, but it is possible - and at least the scrabbling around should feel familiar.
I think this bit of wisdom is often ignored, in this business and many others. Too many people want to continue earning on the same old work in the same old markets. It's foolish to think that you can stand still and prosper, and it's always been that way. Yet for some reason we hear more and more complaints these days from people who aren't trying to change the downward trajectory of their business. Forget about microstock for a second. I personally see this in the design business all the time. Old-school agencies who are annoyed that they can't charge $10k for a brochure design anymore. And not because the market won't bear it, but because they never changed with the market. They want to deliver the same old stale work they were doing 10 years ago and still charge a premium price for it, trading on their experience alone.
I'm not a photographer, but from what I hear from photographers it's much the same trend. Guys who were coasting along 10 years ago suddenly found themselves in tight spots, and the ones who made some moves and were willing to try new things came out ok on the other side. The guys who just wanted to complain about the good old days and refused to try anything new went out of business. I personally know a photographer who was completely against microstock and the whole idea of it about 4 years ago. Today he's still doing contract work, commercial shoots and such, but makes half of his income from microstock. His microstock income filled the void left by the slowing contract work, and enabled him to continue making a living behind a camera.
I'm not saying that microstock is the answer. But change is, at least for a lot of people. We can't always expect to get by while doing the exact same thing we did a few years back. If frequent change isn't something you're comfortable with, any sort of freelance career isn't right for you. You're better off riding a desk and taking a salary.