One of the world leaders walks up to a giant straw hat in the episode in one of the major world government institutions. What is it and how is it related to Luffy.
There is no answer to this question right now, you can only guess what it means and you will find plenty of theories on the Internet.
My favourite theory is that this room contains an item which morphs into the greatest threat for the Tenryuubito. Why do I think there is something that is changing shape according to the threat? Why would the Government (World Leaders - I guess the black silhouette is one of them) contain a bloody straw hat? It only makes sense for me at this point that something is showing the Tenryuubito greatest fear.
I also think it is working like Shirley's predictions: no one knows if its a good or bad omen.
But there are plenty of theories on the Internet.