> Older generation in Hongkong and Taiwan tend to identify themselves as Chinese, but the younger generation tend not to.

I see this, but I also see the "We're [Taiwanese] the real China, and the mainland isn't" mentality as well (they'll get upset if you call them Taiwanese). It does get a bit complicated, especially if you think back to what happened during the cultural revolution and the people that stayed in mainland vs those that went to Taiwan.

Rarely will you run into anyone with this “we’re the real China,” 外省人 identity that would be offended to be called Taiwanese. Descendants of mainlanders that came to Taiwan after 1949 are a minority and Taiwanese identity is very popular here. Both Taiwanese and Waishengren will quickly point out that ROC is the original China and of course they are independent because how could they not be independent from a country that split from it. Then Taiwanese will disagree about whether China (ROC or PRC) has any right to colonize their island.

Another generation and hardly anyone will have Chinese identity, I imagine. An example I hear a lot is that the Vietnamese and Koreans also used to be Chinese.

Taiwanese, Hongkongers, and the larger Chinese diaspora still have the 華人 identity (i.e. part of the Chinese civilization).