I see a couple of possibilities:
They're not going to retire. As they age, if they don't land on a lifelong career and progress the ladder at least a little bit, they'll get to work in physically demanding jobs which will destroy their body and they'll die before traditional retirement ages, or just at where older gens would retire. If they do land into some kind of lifelong career, they'll just work till they die. Think: 85 year old programmers looking up how for loops work again...
Another fun possibility is that they will retire after having started saving at a later date but having no children.
Another one is having small savings and moving to poor countries, Africa may see an influx of such persons once South East Asian countries stop letting them in.
Still time for revolutions and complete changes of systems following armed revolts or wars though..
many possibilities ahead.