> I have been tracking junior software-engineering listings on LinkedIn and Indeed since late 2024.

I don't think such a short timeframe is indicative of anything at all. This data could be interesting if comparing to say before Covid or even before 2008, but as is, this is far too short of a timeframe to draw any actual conclusions. How would you know whether we're currently under hiring juniors or we were previously just over hiring and are now returning to the norm?

2031 is in 5 years. There will be plenty of seniors even if the influx of juniors is exactly 0. Not saying 0 influx of juniors is good, it harms young people. But it wont cause lack of seniors issue in 2031.