How Singaporeans will feel in the future will no doubt be influenced by the growing wealth of China. Remember, China will be a much larger economy than America. With that kind of wealth, many companies in singapore would rather have a pro-China government than not. And corporations very much influence western style governments.
As I have been reading more about Singapore, it is a parliamentary republic (with Compulsory voting!- am I reading that right?). Independent since 1965 its biggest export trading partner is already China (when adding Hong Kong) and China is its second biggest import partner (after Malaysia).
The current political party in power is the People's Action Party -whose leader, LEE Hsien Loong, is staunchly pro-british/american.
But the thing with democracies is their corruptibility by powerful media moguls. That is how the 'orange revolution' happened in the Ukraine. Did you really think a student protest in Kiev could've overthrown election results without extensive media coverage?
It wouldn't be hard for any well funded intelligence agency to influence the elections in Singapore. So their current alliance with Britain is more fragile than people think.
It doesn't have to be a political party supporting re-unification with China. It could just be a political party that supports China and would have Singapore side with China amid growing US-Chinese rivalry. Once that happens, China would lease a naval base in one of the most strategic waterways in the world (and it is THE most strategic waterway as far as the nations of China, Japan, and Korea are concerned).
As for South Africa, it overlooks all trade around the southern continent of Africa. It may not be as strategic a waterway as say the Suez canal, but a large amount of commercial vessels do sail around the Cape of Good Hope.
South Africa currently has good relations with both India and China. South Africa has very poor relations with the US, particularly since George Bush took office. They have been very vocal critics of the US invasion of Iraq, America's middle east policy, and of the West in general for not granting more debt relief for poor african nations.
Nelson's Mandela's harsh criticism of George Bush, even after retiring from office, has caused American relations with south Africa -indeed with nearly all of africa- to enter a deep freeze.