Depend on them for what, the cost of a bowl of rice? What is it exactly about 80 year olds that will collapse a country with a brutal government like China has?
The other thing to look at in those population distributions, besides the upside-down age distribution, is the absolutely pathological gender imbalance. The number of surplus males under 30 should be keeping Xi Jinping up at night because if there is anything that is going to trigger another revolution it is tens of millions of disaffected young males migrating across the country who eventually get fed up with what they perceive as a dead-end future.