> Now, all of this combined: the junior --> senior transition takes say, 5+ years on average (I know, depends). If we move on with the "1/2 senior + AI agents" model, how does a company form a new team? When those seniors move away / retire, who's taking their place? What happens to the velocity of the team without mid-levels now?

> If we let this go on for a couple of years before a reckoning of "oh crap" happens, it'll be very hard to come back from this --> certain "muscles" of the aforementioned seniors will have atrophied (e.g. mentoring, growing others), a lot of juniors (and mediors!) will have left the industry.

> I hope companies will recognize this risk in time...

As someone in an org who has some exposure to legacy support, don't underestimate management's ability to stick its head in the sand until it's too late in order to focus on the new shiny.

I think we're down to two mainframe developers, still have a crap-ton of dependencies on it and systems that have been "planned to be decommissioned" for decades, and at least one major ticking-time bomb that has a big mainframe footprint.