Hong Kong was "leased" to the Brits, who had to give it back after 99 years (or something like that), what kind of fight can the folks at Hong Kong put up that could be significant?
It was only recently that Republic of China (Taiwan) abandoned their plan to retake the mainland, though a pipe dream it was, the people are nevertheless resolute in either staying independent, short of declaring its indpendence as a new sovereign nation, or maintaining its present position, which is somewhat isolated diplomatically. China does not have the capability to launch a major amphibious attack on Taiwan, given Taiwan's qualitative edge, nor would it do so, for Taiwan invests heavily in China's business and industries, China has little to gain by taking it by force. All this saber rattling is just that, saber rattling. I espcially love China's "warning" to the US that we're heading into dangerous waters, as if a third world country was in any position to admonish the only super power on earth.
For Taiwan to reunite with the mainland is to commit suicide, it has nothing to gain and everything to lose. If Taiwan had any such inclination, would China be shooting off missles during the free election there and constantly threaten it will take Taiwan by military means if it had to? It sees Taiwan as a threat, a "renegade province", not a returning child.