My thinking is a bit different here: Seniors, even mediocre ones, already learned a lot of hard lessons by doing things pre-LLMs, even pre-SO. Those skills are valuable and I don't know how to train them into juniors.

I find it easier to get a reasonably smart senior to use AI in a good way, than to train a junior in what thinking to do, and what to outsource, learning basics about good design, robustness and risk analysis. The tools aren't the problem per se, it's more about how people use them. Bit of a slippery slope.

That's just my anecdotal experience from not a whole lot of data though. I think the industry will figure it out once things calm down a bit. Right now, I usually make the bet to get one senior rather than two juniors. Quite different to my strategy from a few years ago.