Earlier quoted context omitted.
Why would China even consider "ejecting" a part of its territory that they fought over for a long time to finally get back? Recovery of lost territories and reunification of the country is a core policy of the Chinese government(s) since 1912... And as noted in the replies, striving for national unity is an ancient theme of Chinese national psyche.
Which I find to be irrational. Stamford Raffles "took" Singapore from the Malay sultanate in the 1820s. In 1963, we finally got it back, but let them go barely two years later due to ingrained cultural differences that manifested during the meantime. With the rise of so many capable cities on the mainland, perhaps pursuit of unification is just not worth the trouble anymore.
This is very different from HK and China.