But open-source software is far more about the process than the product. And therefore longevity of resulting software can be expected to be far greater. Foundations of our software stack - libraries, source control operating systems, compilers, databases and numerous other pieces require people capable and willing to do a long-term care of the software - hence, the community that need to last decades. Linux and PostgreSQL is 35 years old, git is 21, OpenSSL 28.
I believe human-only software development will remain for the foreseeable future, despite the growth of LLM-based ones, just like mass-produced grocery bread didn't displace the artisanal bakeries.