If the burden is too high, there's a risk that future generations will simply decline to care for the elderly who contributed to the problem (childlessness), but then expect the children to care for them in retirement.
The alternative is, more and more resources will be allocated towards the elderly and by consequence less towards kids, making the problem worse with every generation. Not clear though how to break out of this spiral by democratic means if elderly are the majority.
But if the majority voting bloc is geriatric, then that does rather change the fundamentals.