With recent events I've been thinking that bb will be one of the next opponents. Between bb taking coby and possibly law I don't see the luffy waiting much longer to fight teach. But with vegapunk wanting to escape egghead on the sunny to get away from cp0 and Bonney being with them, the conversation with dragon, and kuma trying to run off when lucci mentioned killing bonney, I can see a clash with the wg coming up next even if it's not the final battle against the wg.
Right now my theory involves the strawhats leaving egghead with vegapunk and Bonney and meeting up with the revolutionary army at one of the next islands possibly elbaf. Cp0 following the strawhats and calling for reinforcements for a big battle on elbaf before making it to fullalead to fight blackbeard.
As for rhp and cg I see them competing for the one piece as more of a race than a fight on some island but rather a battle at sea, possibly with imu and his airship trying to stop them all from reaching the final island of laughtale which could be the ancient kingdom that went to war with the 20 kingdoms 900 years ago.