That was the plan. There were all sorts of schemes to develop the African colonies to make them more economically valuable. However, they didn't tend to work out that well (check out the groundnut scheme in East Africa).
The fact is that the territories in Africa were a drain on British resources. It might be possible to give more limited self-government to African countries earlier, but (a) I can't see a British government doing that (Labour or Conservative) and (b) I can't see new African countries keeping the Queen as Head of State.
I suppose a possible way is to follow the French route by binding the new nations to Britain economically in that there will be no development aid unless they remain in Britain's sphere.