There's a fundamental disconnect: OP refers to senior engineers being replaced with AI, whereas the evidence and logical reasoning points much more to junior engineers being replaced by AI. And that premise seems like a quite plausible one...
If industry cared about future seniors, they'd invest in juniors. But that's not what's happening. AI will effectively replace seniors in 20 years with the current trajectory. Whether or not that replacement is adequate or not is the bigger question.
It's junior level coding and maybe senior level advising, but even then only when clearly directed with the right questions and guardrails.
As an autonomous thing? Junior at best.
That's why I think it's extremely helpful for seniors: with proper guidance, it really boosts your productivity, writing notable parts of the code.