I'd add significantly more euro populations to the rhodesias, south africa, kenya, Tunisia, Angola(if only because of intermarriage), mozambique(intermarriage), portuguese guinea(see Angola+Mozambique), Beuchanaland
My estimates were pretty conservative and I went off of migratory trends. For Southern Rhodesia, it's peak migration was around 15,000 net European migrants per annum in the early 1950s, this only lasted 5 years though. I'd assume Southern Rhodesia could attract 10 to 15,000 net migrants indefinately given good economic conditions.
Northern Rhodesia's European population peaked at 77,000 around 1959. Here peak immigration was in the early 1950s with most European settling along the copperbelt. One thing hampering European colonisation was the British government's refusal to allow Europeans to own land in the protectorate. If the restrictions are eased, the Northwestern area around Abercorn (Mbala) would probably have at least 5,000 Europeans.
For South Africa the peak number of net European migrants was reached in mid-1970s at around 50,000 in a single year. It began to fall in the mid-1980s so that the country had a net emigration. The Verwoerd government estimated that the European population would reach 8 million by 2000. However, that would have meant maintaining the high immigration levels of the 1960s until 2000. I think the maximum for South Africa is about 10 million.
For Kenya, this colony was never too successful at attracting Europeans. It had a powerful European minority that never reached 1% of the total population. The peak was around 3,000 net migrants. There were only 67,000 Europeans at independence. The major reason was the country was home to 200,000 Asians and Arabs that filled the roles of merchants that many Europeans did in other colonies (the same was true in Uganda and Tanganyika), this left Europeans as mostly large landowners and upper level civil servants. So I think 500 to 600,000 is probably a bit too generous.
Tunisia much like Algeria had a peak of Europeans in the 1930s. Few French were willing to settle in North Africa and the French government was hesitant to allow more Italians in (for obvious reasons), the European population was 255,000 in 1956 and 2/3 were ethnic Italians. French Morocco seemed to be mroe popular up until the outbreak of violence there in the early 1950s for French settlers.
For Angola I did not include the mixed race population in the total. The mixed race population would probably be around 400,000 to 500,000. In OTL Angola managed to attract over 25,000 Portuguese settlers in 1973 alone. The annual average was around 12,000 from 1955 to 1965 and 20,000 from 1965 to 1973. So my calculations are 1 to 1.25 million given that Angolan whites had a relatively high birthrate of 3.6 children per woman. If Angola were still Portuguese the settlement schemes would continue to this day. In OTL the Portuguese government began in the early 1950s building towns with agricultural settlements around them where they would settle Portuguese people from specific villages in Portugal or Cape Verde and try to replicate rural Portugal in Angola (and Mozambique too). The Cunene River scheme in southern Angola was started in 1972 and never finished for obvious reasons, was a joint Portuguese-South African hydroelectric project where 200,000 Portuguese were to be settled by 1995. Below is a link to a typical settlement: Cela, begun in 1952.
http://www.sanzalangola.com/galeria/albuo44?&page=1
Mozambique has fewer mixed race individuals than Angola. I'd assume with a European population of 700,000 there would be around 200 to 250,000 mixed race individuals, including Cape Verdians. Mozambique never attracted as many settlers as Angola and the peak was around 16,000 in 1972. As in Angola there were major colonisation schemes underway in the 1970s. The largest being the Cabora-Bassa Valley which was to provide farmland for 100,000 Portuguese settlers by 2000 and the Niassa colonatos (settlements) which were begun in 1973 in the province of that same name in Northwestern Mozambique.
Portuguese Guinea was never a settler colony. The 5,000 Portuguese who lived there in 1973 lived mostly around Bissau. There were 10,000 or so mixed race individuals, but most were Cape Verdians who settled in the colony and worked as civil servants.
Bechuanaland was never a settler colony. It was something of a wasteland with fewer than 5,000 Europeans in the protectorate in 1966. It was so neglected that it was administered from Mafikeng (South Africa) until 1965. Perhaps with the discovery of diamonds it could boom, but I'd assume it would be incorporated into South Africa.
I just thought perhaps a colonised Africa begins to mirror the U.S. southwest of today. Cheaper land and unskilled labour prices turn parts of Africa into booming areas much like Arizona, Texas, Nevada, Georgia etc. With airconditioning after the 1960s it's very possible. Africa could become the subelt of Europe. With African unskilled labour filling much the same role of Mexican labour in those areas.