There are two problems here.
1. The industry cannot define the terms junior or senior.
2. Most seniors today are the prior generation’s juniors with almost no increase of capabilities, just more years on a resume.
The article asks about what happens when today’s seniors retire in the future. I would argue we are at that critical juncture now.
Retire? I can never retire. I'll likely die at my keyboard. Software has not provided the future I was hoping for.