What will happen is pretty obvious. Those companies will either be classified as too important to fail and get government support or go bankrupt and will be bought for pennies on the dollar. For the customers nothing much will change since tokens are getting cheaper every year and the business is already pretty profitable. Progress will slow down massively till local open weight models catch up to pre-crash SotA and go on from there.
ChatGPT 3.5 came out coming on 4 years ago now. I don't think a human generation (~20-30 years) needs to be the benchmark here, but new juniors in the industry for a handful of years can be said to be a whole "generation". That how I was reading OP.