I think the new frameworks and technologies could theoretically help everyone equally. I don't really feel threatened by that, just learn new stuff every now and then.
Overall I find that big companies aren't that eager to adopt the very newest technologies, so no need to learn everything right as it comes out.
As for age... My older colleagues are generally more experienced and productive than the young ones, so at least there's that. But there's probably some diminishing returns - one gains more productivity in the first 5 years than from 15 to 20 years.
Overall it's very possible that supply outgrows demand at some point. And coding salaries will surely go down in that case. But I don't personally feel we're close enough to that to start working on a exit strategy.
Also, for me personally, I am pretty obsessive about coding, so I learn quite some new stuff all the time. There's lots of other coders who see it as a good enough career, but not more than that. So I am hopeful that they'll quit before me, should demand for programmers decrease.