The plan is to make the AI a little better so that it can do to the seniors what it did to the juniors.
Without senior developers having a deep understanding of the problems underlying the systems, they'll have little to distinguish themselves from non-skilled management poltroons, who are themselves even more replaceable by agents. But the alignment problem will become even more severe.
Software do have lot of variables, real world edge cases and unknowns, I don't think 100% automated agentic development is a good things. I know you wrote it sarcastically.