I think this is an excellent point and that the idea of a vaccine as a "cure" is a bit misguided.
As I understand it, (and please, someone correct me if I have this wrong) the Coronavirus acts much like other viruses in that it can reoccur. Just like we have "flu season" every year, COVID-19 has the potential to be something that comes around again, even after the curve has largely flattened.
A Vaccine, if and when it is developed, will help in keeping people from contracting the virus, but it won't do anything for people already infected and it's not likely to be 100% effective in preventing new cases either.
I believe social distancing is destined to be the new norm. There will be situations where being in close proximity to others is unavoidable (trains, buses, etc) but things like shaking hands are going to become a thing of the past.