Intensive agriculture with fertilizer, pesticides, and machines has been slow to catch on in sub-Saharan Africa. This combined with high unemployment means a return to subsistence agriculture is likely in the long term if there is no other intervention.
The problem is traditional methods won't produce enough food to feed Africa's population. It seems the only options are increasing dependence on food aid and imports or letting disease, famine, and war restore the balance. There are 1.6 billion people in Africa now, but only 140 million when they were self-sufficient for food in 1900.
Alternatively, there could be a mass migration out of Africa, but most countries would be reluctant to accept large numbers of them.
Birth control could help, but it too has been slow to catch on, though there has been a gradual decline in fertility over the past century.
Another option would be to allow foreign farmers to buy land in Africa and raise crops. This would be unpopular, but it would solve the food shortage problem. Neocolonialism to the rescue?
China may become the star of neocolonialism. If Africans let them build infrastructure, they'd probably let them farm. China needs food imports and also has a large pool of unemployed young men. I can see Zimbabwe letting Chinese workers grow food on formerly white-owned farms. South Africa might do the same. The Chinese would have to hire enough Africans to sweeten the deal or provide some other incentive.
When I was in Tanzania, I saw that pretty much everyone was a farmer, and most were pretty good at it. I tried my hand at it but only succeeded in growing a small bunch of bananas. Hivyo ilivyo (that's the way it is).