My own observation is largely of people in my age group where the tide is outward, no one I can think of has come back but I appreciate that people will come to HK if there is opportunity for them. Some in my age group are essentially leaving to acquire passports (British or Canadian) and say that they will return once they do. Those who are staying still see opportunities here for now but even some of those ones say that they would leave if better opportunities came up.
Some business people who I know want to have their feet in places out of HK to keep their options open. HK no longer has 100% confidence, everyone has backup plans in their pockets.