TAIPEI—No matter how desperately China hankers for unification with Taiwan, a strong conviction that time is on its side has long trumped its temptation to use bullying tactics to force the outcome.

Eventually, the Chinese thinking goes, the Taiwanese will come to the conclusion that their future lies in economic integration with the mainland, and that once the two economies are thoroughly enmeshed a political settlement will end an estrangement that has lasted since 1949, when the Kuomintang retreated to Taiwan after losing...