Taiwan, the Republic of China, will never peacefully 'surrender' to the communists. So there is no prospect of peaceful reunification as long as the CCP holds power on the mainland.

The CCP/PRC knows that very well so there is no point for them to allow HK to persist, especially considering that this could give ideas on the mainland ("if HK can have this, why can't we?")

(Also, no-one ever talks about Macao, but it's the same as HK)