OP: Your question suggests that role of SET ("a programmer developing tests for designed system") is being replaced by something else, but your questions does not mention with what.
Automated testing is NOT going away, so some companies will call it by different names but concept ("a programmer developing tests for designed system") is here to stay for foreseeable future.
What might change is tools and methods it uses, and how company calls that position. So as always, be prepared to learn new technologies (or, as you said, be "left in dust"). For a competent, skilled programmer there is nothing to be worried about (except general AI), but also there is not shortcut, no silver bullet. You have to continue to run on the technology treadmill, as some technologies are becoming obsolete and being replaced with new ones.
Who might be worried is a semi-competent apprentice (code monkey) who barely learned single technology and stopped learning (or instead of consistently enhancing his skills by honest hard work, is trying to find unfair shortcuts, technological silver bullets, which will give him advantage without work. There is no silver bullet. All there is: hard work to keep up.
I know, it is a delicate balance between keeping up with new technologies, and being so obsessed with them to the point using unproven non-mature technologies in production with disastrous results (or forced upgrades/conversions).
To avoid mistakes, you need good judgment. To have good judgment, you need to learn from past mistakes. There is no replacement for experience.
Until developing general AI and self-conscious, self-programming, self-improving systems, someone has to test the code. And few weeks after developing such general self-improving AI, human civilization might be over, so it would not be a problem.