How about you answer what if he did *not* declare that any of the conciliar popes were not popes?
You said that it is *absolutely* possible that a future pope declares the Conciliar popes to have been false popes. What would be the reason for him to do so? Do you think that a pope simply declaring a prior Pope to have been a false pope actually means that he was a false pope? Or is there some sort of criteria that needs to be met to make the popes declaration true?
To your question, if you mean that a future Pope simply remained silent on the Conciliar popes, while condemning V2, the Novus Ordo, the rest of the new sacrament, etc. then the matter would remain an open question. But I do not believe that will happen.
If you mean a future Pope actually declaring them to have been true popes, while condemning V2, the NO, the rest of the new sacraments, etc., I do not believe this will happen either. In fact, I admit no possibility of this happening, I would say I am morally certain it will not happen. But you say that it is absolutely possible that a future Pope does declare the Conciliar popes to have been false popes