In 1997 the Communist dictatorship in Bejing promised the people of Hong Kong that they'd have local autonomy, including electing their own officials, after the British colony was forced to rejoin China. In 1994, Russia, then a corrupt democracy and now a corrupt dictatorship, promised not to use force or threaten to use force against Ukraine in return for Ukraine giving up its nuclear weapons.
We know how both these promises worked out. You can bet that no country is going to give up its nuclear weapons. any time soon. And Taiwan is even more unlikely than before to join China on the basis of the promise that Beijing would allow the people of Taiwan their own democracy.
Dictators think promises are a joke.