Oda seems to be setting things up so that all of the Yonko have 3 of the 4 RP, and will be going after the last RP at the same time, which will kick off the final war in a battle royal between the Yonko. Zoro will most likely fight Mihawk during this conflict, and then the Marines/WG will get involved to stop the Pirates who have all 4 RP, which will continue the battle to Laughtale where Zoro will fight Garling or Venus.