B
what can possibly happen here that will shake the world.
Either:
1. The newly declared Yonko gets packed by the Navy, once more showing to the populace how the WG has the upper hand and therefore the means to protect them from the evil pirates;
or its opposite:
2. One of the three greatest forces of the Navy, Admiral Lightspeed, is defeated by the son of the leader of the evil revolutionaries, which means that everything is doomed and the system might soon be forced to change, if not fall entirely.
Else Oda can keep it slightly more contained and simply announce to the world that:
3. The ruthless Mugiwara just murdered their head researcher, the man from the future who alone could've cured famine and all other ills Average Joes are afraid of.
Even if Luffy were to punch and/or defeat Saturn, I don't think the event would be made public.