I know why you're wondering about this, Jeanne, and I also think this depends on the background of the person(s) involved, and of how hard pain/control we're talking of. If it's really into the sadistic/consensual abuse range - hard bondage, flogging, clit clamps and aggresive cum denial, then I think the step from vanilla to top might be the longer one, because once both parts have accepted and got into the element of real deep pain and submission, it might not be such a huge step to extend this Dom mode to a bigger part of everyday life, making the sub a 24/7 owned slave who can be brought to her knees, mentally or physically, more or less anytime, or at least who has few safe/cordoned-off areas of life in which she would never be touching at her submission
This doesn't mean that the couple are not able to adjust and weigh in a normal outside life (kids, friends, work, relatives, vacations) too, but the Dom (often, the man) takes on a wider Dominant role: Tessa for instance knows about that. Which is, I guess, something that has a pull on both of us, and then we'll see how far it's a workable reality.