Well, after Beijing 2022 there are currently no Games in Asia as I expect the Winter Games 2030 will be awarded somewhere to North America. As for hosting 2028, I would bet on to host 2030. So if there are no Games in Asia for about 10 years, I would guess that Seoul has high chances to be selected. Also for 2034 Winter Olympics, my favourite is , probably Sapporo. After 2036, there is a possibility to be another edition of the Olympic Games in Asia or would again return to Europe/America and maybe even Australia.
As for African countries, discussion about has already been going on here so also in my perspective it is the most possible country on African continent to host the Summer Olympics. But I am also afraid there would have to be done a lot which may meet a lack of funding and public protests.