They already have more pensioners than children being born. The same trend can be seen in virtually every single developed country. We are soon to going to not be able to afford to pay these pensioners if there are not enough people paying taxes. Hopefully you don't actually think pensions are somehow grown on trees.
Yes, we can print the money and the world won't end. There's not some automatic hyper-inflation that happens when money is minted. There's so much around already you see.
Think of cash as points in a game. If we keep playing games, racking up points, the points don't necessarily become worthless. They may change a little as confidence varies.
It's not about the imaginary points. Its about the goods and services. Goods depend, these days, mostly on automation which isn't going away. So little problem there.
That leaves services. Yes, they depend entirely on human capital. So we're going to have to automate, train assistance animals, or use technology to do away with the need. Especially among the elderly who traditionally require more services.