Sure. But that's not what keeps systems written in COBOL or MUMPS. It's not what's kept the US air traffic control system running on 1970s-era hardware and so

Sure. But that's not what keeps systems written in COBOL or MUMPS. It's not what's kept the US air traffic control system running on 1970s-era hardware and software until very recently. Humans are perfectly capable of rewriting these systems. AI will be, as well. The problem with changing a mission-critical system is risk, and cost. Maybe omniscient AIs in 3023 won't have this issue, but my ghost will be entirely unsurprised if there are still mission critical systems written in C laying around because whatever benefits are rewrite would give are dwarfed by the risk, perceived or real, of what happens if the rewrite isn't 100% perfect or doesn't 100% match the current system.