It is clear as day that the WG are the final villians, it's been build up for year now, in every arc we get into these days , it just shows more and more the dark side of WG, once they discover the void century's real history then they are going to fight the final war in this manga, that is the war against the WG, oda said himself that in the last war the world will be thrown in a huge turmoil during the last war.
BB was never portrayed as the FV, he is somehow the antithesis of luffy, both of them want to reach OP and the pirate king title but in different ways, BB is just the pre-final enemy for luffy that will help luffy grow enough to be the PK and together with the dark history to challenge this world into a fight, its been made pretty obvious by WB that raftel is not the final point or the PK title, there is something more than that, just look at this speech:
[video=youtube;bFb5h9hl9Ig]https://www.youtube.com/watch?v=bFb5h9hl9Ig[/video]
It pretty much tells that a "D" will find the treasure and after he finds out the true history he will challenge the world into a fight, the organization that has hidden all those decades for some reason, the moment the structure and the system of WG, and most importantly when the mariejois is destroyed its the final point of the manga.