I can see Sanji and Zoro getting the same bounty after Wano. I advocate for this to happen. It will give Zoro fans a headache. I don't know why this would be a problem. Both Sanji and Zoro have been portrayed as equals throughout the series. If their is a gap between their new bounties, it will be small. So if anyone forecast Zoro having a 1.6 billion bounty then Sanji will have something like 1.55 billion or 1.65 billion.