For whomever follows my TL the Great Turk Returns, I have not decided on the fate of South Africa yet. For you to decide. There are three options:
Netherlands: The area is still Dutch. It is ruled by the VOC officials in the East Indies in a very decentralised manner. Nominally it is Dutch territory but the Netherlands being under French Rule makes it hard to assert rule over there. Dutch government in exile claims the region and accepts to make Cape Town a Free Port. The Dutch colonist may accept the exiled King as their ruler again but if he regains his throne. In a future scenario, Dutch South Africa might be an alternative for the Americas or Pacific.
United Kingdom of Great Britain and Ireland: There is no secret that London desires the Cape. However, the VOC in Cape Town being loyal allies to Britain and not to alienate the exiled Dutch Royal Family, Britain makes no move YET. They try to persuade the Dutch to give it to them and to be compensated. Gaining South Africa makes the British the biggest Colonial Power in Africa.
Independent Cape Colony (under Anglo-Dutch Protection): A third alternative is an independent Cape Colony under large British and small Dutch protection. Both nations have priority advantages in the Cape. But rule over the Cape is left to the local Dutch Colonists in Cape Town. This avoids conflicf between two States but it is in danger to fall in influence of other Powers (France, Spain etc...)