Who is the person Caribou talking about??

 

In chapter 1056, we saw Caribou was present in Wano and and he heard about pluton when straw hats were talking about it. Caribou then refer to a certain person who'd be interested in pluton and Poseidon.

Who is that person? Someone who is interested in ancient weapons. 

I think the person Caribou talking about is Buggy and here's the reason why.

We know that buggy has formed a very powerful organization with Crocodile and Mihawk and they are putting bounty on marines. Buggy on getting ancient weapons will be so dangerous for marine. We also know that buggy is a character who is interested in powerful people and weapons.

Also, Crocodile is with him who was finding pluton in Arabasta and most probably he is still interested in them, I am sure he will try to get ancient weapons by the help of Buggy and Mihawk.

And Caribou can get high commission for telling information about pluton and Poseidon to Buggy.

So most probably the person Caribou talking about is Buggy.