I strongly agree about the disparity in the birth rate — that’s a lesson sociologists around the world should never forget.
About Taiwan, they might indeed invade — not because there’s a national demand to take back what they claim is a rebellious province, but because they’ll have forced themselves into doing so.
It’s the same dynamic seen in the GOP for the past 40 years — no one’s allowed to criticize the powers that be, and no one’s allowed to suggest that liberals might be right about anything ever. As a direct result, politics within the GOP has become a never-ending cycle of “I’m more conservative than the other guy” to the point where the principles of true conservatism have been long forgotten.
In China, since no one’s allowed to be openly critical, those in charge are not just empowered to do what they will, but increasingly feel pressure from within their ranks to bring Make China Great Again. It’s this dynamic that I suspect might be the factor most likely to force them to invade Taiwan.