AFAICT, the Chinese administration believes it must reunify Taiwan; they've backed themselves into a corner with their rhetoric. They haven't because they believe it's better to wait because the chances of it happening militarily or peacefully are greater in the future than they are now.
But if it's going to be harder in the future, they must invade now.
Luckily I don't believe your argument holds.
Taiwan's birth rate is roughly similar to China's, so it doesn't really affect their relative positions.
China's debt is 85% sovereign so it's not a forcing factor either.