I read through the entire part ?, with the footnotes and I still think I am right.
All this means is that the future Bais Din HaGadol can overturn the halacha and be koveya like Bais Shammai, and given their additional gadlus in chochma it is likely they will overturn some of the psak. But it is unlikely that they will overturn all of it and certainly, short of removing their bechira and individual n’tiyas neshomo, there is no way to guarantee that they will pasken like Bais Shammai in every instance.