This is an issue that would have to be decided by the Constitutional Conference. However, what follows below gives some guidance.
People who were born in the Cape would have automatic citizenship. As regards people who live in the Cape at the time of independence, but who were not born in the Cape, their rights to citizenship will be decided by the Constitutional Conference.
After independence people who want to immigrate to the Cape must follow the same procedure as is the international norm on immigration, i.e. must apply for immigration and become a permanent resident holder first. Only after a period of 5 years can one apply for citizenship (remember citizenship is not a right of a permanent resident).
Any other visit for business or pleasure, work, study, etc. must comply with international standards on the issuance of a valid non-immigrant visa for the appropriate visit.