This is a hard question to answer because it depends so completely on definitions of readiness, and that is primarily a political debate. Most Africans would tell you that they were always ready for independence, and colonialism was always illegitimate. More conservative factions in Europe certainly thought that African countries were not "ready" at the moment of decolonization.

Perhaps a better way to frame the question would be to ask whether European powers in Africa invested in institutions to allow a smooth transition from colonialism to independence. The answer to that question varies widely across the continent. The DRC, Angola, and Mozambique are the classic examples of European powers not preparing for a transition, with pretty bad results. Ghana and Senegal would be counterexamples.