Alternatively: if AI makes a good developer 2x more productive (which I do think is possible based on my own experience), developers are now 2x more valuable to employers. The cost of building software drops in half, which means employers that previously wouldn't have developed their own software (too expensive) are now in the market for custom solutions. Demand for developers goes up.
If you believe that making developers 10% more productive results in a need for ~10% less developers, why didn't open source software over the past ~20 years harm our profession?
Working with open source packages from npm and PyPI has given me WAY more than a 10% boost - so much stuff I don't have to write from scratch now!