I would question the assumption that "in many countries around the world, especially in Africa, the people natively speak both an indigenous language and French due to French colonization". It is correct that French is an official language in a number of former colonies, but I believe the assumption that the populace of D.R. Congo, for example, natively speak French is untrue. First, there is a difference between natively speaking a language, and learning a language to a reasonable degree of fluency in school. Second, especially in Africa, there is a difference between the linguistic habits of the urban intelligentsia and the habits of the general population. French is widely used with the middle and upper class in francophone cities, but not so much with rural farmers. Also note that among educated city-dwellers in Africa (esp. Cameroon or Cote d'Ivoire), francophones often do not natively speak some indigenous language, instead, they just speak French (and maybe know enough Bamileke to talk to grandma). Whether or not French ultimately expands or contracts in the former colonies depends largely on the extent to which formal education expands to transplant the urban experience into rural areas.
An obvious difference between England and the former French colonies is the amount of time between the departure of the French (finessing a few assumptions about "French" and "departing"), which alone could account for any actual difference in the status of French in these cases. A less obvious difference is the vastly different statuses of formal education (not important in Medieval England, quite important in modern Africa).