When I'm asked "what if it changes?", I usually answer with something like "we'll solve it when, and if, it happens". I'm a fan of solving the task at hand, not more, not less. If I know for sure that we're going to add feature X in a future version, sure I'll prepare my code for its addition in advance. But if I don't know for certain whether something will happen, I act as if it won't. It's fine to refactor your code as the problem it solves evolves. You can't predict future, and you'll have to be able to deal with mispredictions if you try, too.