Sofala had seemed promising early on, particularly as the Portuguese traders hoped to obtain gold from the interior, but it was soon relegated as nothing more than a place to obtain ivory. It's major disadvantage however, was that its anchorage was too shallow, being considered unsuitable for the naus of the Portuguese ships. By the mid-16th century Sofala was a backwater though Afro-Portuguese traders known as "moradores" occastionally sold ivory to Mozambique. In 1589, Captain Estevão da Veiga, survivor of the shipwreck of the "S. Tomé described the region as having "some villagers who had Portuguese names and spoke Portuguese because, “sometimes, though not very often, Portuguese traders came to buy ivory”. In 1634, Dutch pirates were able to rob some Portuguese traders in Sofala, but it is possible that land south of remains in the Portuguese sphere even if the VOC capture Mozambique. By 1650 the Viceroy in Goa, Vasco Mascarenhas, recommended that the fortress at Sofala be demolished to prevent it from falling into Dutch hands, being seen as of little value.
The Portuguese might manage to maintain a presence in Southeast Africa after a Dutch conquest of Mozambique Island, not unlike that in Portuguese Timor. The Afro-Portuguese "moradores" might continue to eek out an existence with very little economic activity taking place, making it able to survive until a peace is established with the Dutch. A nominal Portuguese presence in the region might lead to the Portuguese eventually establishing more formal control at a later date.
One of the important effects of a Dutch Mozambique in Asia is that the VOC focusses greater efforts on trading between East Africa and the Middle East. The domino effect of the fall of Mozambique could resemble that of the Portuguese in Ceylon and Southern India during the last years of the war with the Dutch, with one fortress after another falling to the VOC. This might make the Konkan Coast the jewel of the Dutch Empire (rather than Java). Diu, Bombay and Goa might fall to the VOC, and a larger Dutch India is certainly a possibility. After the loss of Mozambique and possibly Goa, the remaining Portuguese traders focus on the "outer route" around Madagascar and trade with Bengal and the Coromanel Coasts and perhaps the Malabar Coast while if they can retain a presence there, assume greater importance. A retreat to Malaca and Macau could make it so that those are some of the few remaining Portuguese relics in Asia.
In "Mozambique Island:The Rise and Decline of a Colonial Port City" author Malyn Newitt says the following on page 119.
"Portugal’s successful defence of Mozambique had a long-term effect on the development of european empires in the east. unable to secure control of the Mozambique Channel the Dutch now concentrated their efforts on Indonesia rather than India and their ships took the ‘outer passage’ to the south of Madagascar. In due course they established bases at Batavia, Mauritius, andfinally the Cape of Good Hope in 1652 leaving Portugal in control of the Mozambique Channel, the East African coast and the northern sea routes to India."
This would be my most likely way to achieve a Portuguese South Africa, meaning that lucrative Mozambique is lost and of course that would have repercussions in Asia.
