So wrt rehiring and the golden age of pilots to return being 40... yes... this is true... but understand that there are multiple factors in play here...
Agreed, the 40 year olds have a decent experience level and 20-25 years of flying left in them. Whilst the under 30s are able to move back to jobs in their own countries and start at the bottom of the seniority list, someone 40+ especially with a family, will be locked into the airline and it will be much harder for them to start over if they leave.
50+ would be mainly trainers, examiners or managers.